Name of invention: Casting equipment and casting method
Technology field
[One]
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 manufacturing clean steel.
Background
[2]
Generally, inclusions such as alumina (Al 2 O 3 ) are generated in the molten steel of the ladle due to the reaction between aluminum (Al) and oxygen (O 2 ) during the steelmaking process . The inclusions solidify together with the molten steel during casting of the cast, which causes product defects during rolling.
[3]
For the generation or removal of inclusions such as alumina (Al 2 O 3 ) in molten steel in the ladle , in a vacuum degassing facility (Reinstahl Huten Werke Heraus, RH), Ladle Furnace (LF), in a tundish process during casting operations An inert gas such as Ar gas is blown into the molten steel to remove inclusions.
[4]
On the other hand, the ladle that received the molten steel after the smelting using a vacuum degassing facility (Reinstahl Huten Werke Heraus, RH) or the temperature rising using a Ladle Furnace (LF) was supported by a ladle turret to support the upper tundish. Is located as That is, the ladle turret is provided with support portions that can be seated on both sides of the swing tower, and the ladle is seated and supported on each support portion. Then, the two ladles are alternately transferred to the tundish upper part by the rotation operation of the swing tower. Here, among the two ladles, the ladle positioned above the tundish is the ladle participating in the casting, and the ladle positioned outside the tundish is the ladle waiting for the next casting.
[5]
By the way, even when refining using a vacuum degassing facility (Reinstahl Huten Werke Heraus, RH), heating operation using a Ladle Furnace (LF), or blowing Ar gas in a tundish, when the ladle is in the atmosphere or casting to the ladle turret Since inclusions are generated, defect problems caused by inclusions still occur.
[6]
To this end, in the Korean Utility Model Publication 1998-033102, Ar gas is injected into the ladle that is not in standby or participating in casting. In the case of this method, it is possible to promote the separation and floating of inclusions present in the molten steel, but there is a problem in that the generation of natang is increased in the molten steel bath surface, thereby accelerating the generation of re-oxidizable inclusions.
[7]
In addition, since no Ar gas is blown in during casting, there is a problem that inclusions are still generated in molten steel in the ladle participating in the casting.
[8]
(Patent Document 1) Korean Registered Utility Model Publication KR0332894Y1
Detailed description of the invention
Technical challenges
[9]
The present invention provides a casting equipment and a casting method capable of reducing inclusions.
[10]
The present invention provides a casting facility and a casting method for reducing inclusions by injecting gas into the turret in the atmosphere or during casting.
[11]
The present invention provides a casting equipment and a casting method for suppressing or preventing the occurrence of sugar.
Task resolution
[12]
Casting method according to the present invention The process of placing the ladle containing molten steel in each of the upper side of the tundish and the outside of the tundish; Supplying molten steel of a ladle disposed at a casting position above the tundish to the tundish to perform casting; And a step of blowing an inert gas into the ladle disposed at the casting position.
[13]
The process of injecting the inert gas into the ladle disposed at the casting position includes: injecting an inert gas at a first flow rate into the ladle disposed at the casting position to open the ladle at the casting position; It includes; after the ladle of the casting position is opened, when casting to supply molten steel to the tundish is initiated, a step of blowing an inert gas at a lower flow rate than the first flow rate to bubble it.
[14]
In bubbling the ladle in the casting position, the inert gas blowing flow rate decreases as the molten steel height in the ladle in the casting position decreases.
[15]
The current molten steel height (L 1 ) relative to the initial molten steel height (L 0 ) before supplying molten steel in the casting position ladle to the tundish in reducing the inert gas blowing flow rate as the molten steel height in the ladle at the casting position decreases . It is supplied at a flow rate (m 1 ) calculated by Equation (1) using the ratio and the initial gas injection flow rate (m 0 ) when supplying the treadmill to the casting position ladle .
[16]
[Equation 1]
[17]

[18]
The initial gas injection flow rate (m 0 ) is preferably 1 LPM or more and 20 LPM or less.
[19]
And injecting an inert gas into the ladle disposed in the standby position outside the tundish.
[20]
The process of injecting the inert gas to the ladle disposed in the standby position may include: injecting an inert gas at a first flow rate into the ladle arranged in the standby position to open the ladle in the standby position; It includes; after the opening of the ladle in the standby position, when casting is started to supply molten steel to the tundish, a step of blowing and inert gas at a second flow rate lower than the first flow rate to bubble.
[21]
The first flow rate is preferably 80 LPM or more and 200 LPM or less, and the second flow rate is preferably 1 LPM or more and 20 LPM or less.
[22]
Foundry equipment according to the present invention is a tundish temporarily storing molten steel; A turret device having a pair of support portions for supporting a pair of ladles in which molten steel is accommodated, and alternately positioning the pair of support portions in a casting position above the tundish and an atmospheric position outside the tundish. ; A mold positioned below the tundish to solidify molten steel provided from the tundish; And a gas blowing device connectable 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 in the standby position and the ladle supported in the casting position on the turret device.
[23]
The gas blowing device includes: a first blowing line connectable with a ladle supported at the standby position; A second blow line connectable with a ladle supported at the casting position; And a first supply part connected to the first blow line to selectively supply an inert gas to the first blow line at a first flow rate for opening the ladle in the standby position and at a second flow rate smaller than the first flow rate. ; And a second supply part connected to the second blow line and supplying an inert gas to the second blow line selectively at a first flow rate for opening the ladle in the casting position and at a smaller flow rate than the first flow rate. do.
[24]
The inlet gas is supplied at a first flow rate of 80 LPM or more and 200 LPM or less to the first blow line so that the inlet of the ladle in the standby position is opened, and after the ladle in the standby position is opened, the first blow Inert gas is supplied at a second flow rate of 1 LPM or more and 20 LPM or less to the line to bubble the ladle in the atmospheric position.
[25]
The second supply unit supplies an inert gas at a first flow rate of 80 LPM or more and 200 LPM or less to the second blow line so that the inlet of the ladle in the casting position is opened, and the ladle in the casting position is opened Then, when the molten steel in the ladle at the casting position begins to be supplied to the tundish, the inert gas according to the drop in the molten steel height in the ladle at the casting position, in a lower flow rate range than the first flow rate to the second blow line. Reduce the blow flow rate.
Effects of the Invention
[26]
According to the embodiment of the present invention, an inert gas is blown in when the ladle is in the standby position on the turret device and during casting to supply molten steel to the tundish. Accordingly, inclusions can be reduced compared to the prior art, and clean steel can be produced. That is, when the ladle is in the standby position, by initiating fine bubbling after opening the ladle, it is possible to reduce the occurrence of inclusions in the atmosphere. In addition, by injecting an inert gas into the ladle L during casting, it is possible to reduce inclusions in molten steel in the ladle during casting.
[27]
In addition, as the flow rate of the gas is decreased as the height of the molten steel decreases during casting, it can be bubbled in an appropriate amount, and thus, it is possible to suppress or prevent the occurrence of spewing due to the inert gas. That is, when the gas is blown at an excessively large flow rate relative to the amount of molten steel or the height of the molten steel, slack may be generated in the slag of the bath surface due to vortex generation due to gas injection. L) By adjusting the gas injection flow rate to correspond to the decrease in the height of the molten steel, it is possible to suppress or prevent occurrence of spouting due to gas injection.
Brief description of the drawing
[28]
1 is a view showing the main parts of a casting equipment according to an embodiment of the present invention
[29]
2 is a view showing a ladle according to an embodiment of the present invention
[30]
3 is a schematic diagram showing a gas blowing device according to an embodiment of the present invention
[31]
4 is a graph showing a method for blowing gas in accordance with an embodiment of the present invention to the standby ladle
[32]
5 is a graph showing a method of blowing gas according to an embodiment of the present invention to the ladle being cast
[33]
6 is a view showing the results of sprinkling when bubbling in a method according to a comparative example ladle being cast
[34]
7 is a graph showing the amount of inclusions in each operation step as an inclusion index (Inclusion index)
Mode for carrying out the invention
[35]
Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in various different forms, and only these embodiments allow the disclosure of the present invention to be complete, and the scope of the invention to those skilled in the art. It is provided to inform you completely.
[36]
[37]
The present invention provides a casting equipment for reducing or suppressing the occurrence of inclusions and sprinkling by injecting gas into the turret device in the atmosphere and casting ladle, and casting method using the same.
[38]
1 is a view showing the main parts of the casting equipment according to an embodiment of the present invention. 2 is a view showing a ladle according to an embodiment of the present invention. 3 is a schematic view showing a gas blowing device 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 to a standby ladle. 5 is a graph showing a method for blowing gas according to an embodiment of the present invention to the ladle being cast.
[39]
[40]
1 and 3, the casting equipment according to the embodiment of the present invention is capable of supporting a pair of ladles (L) in which molten steel is accommodated, and a turret that moves a pair of ladles (L) by a rotating operation. The apparatus 100 receives the molten steel from the ladle L moved to the upper side, receives the temporarily stored molten steel in the tundish (T), and the tundish (T) to temporarily store it and cools it first to give a constant shape. A plurality of segments (20), tundish (T) performing a series of molding operations while secondary cooling the primary cooled cast steel provided in the lower part of the mold (M) and the mold (M) for initial solidification It includes a gas injection device 200 for injecting an inert gas to each of the ladle (L) positioned on the upper side and the ladle (L) waiting outside the tundish (T). In addition, the shroud nozzle (SN) that supplies molten steel of the ladle (L) to the tundish, the gate that controls the communication between the ladle (L) and the shroud nozzle (SN), is located on one side of the tundish (T) tower It includes a nozzle mounting unit 30 that connects between the nozzle and the shroud nozzle.
[41]
[42]
The aforementioned ladle (L), turret device (100), tundish (T), mold (M), and segment (20) are similar or identical to a general continuous casting facility, and thus detailed description thereof will be omitted or briefly described .
[43]
The turret device 100 is a rotation driven swing tower 110, and is formed to be extended in both directions around the swing tower 110, or disposed to be located on both sides around the swing tower 110, respectively The ladle (L) includes a pair of support portions 120 that can be supported or seated. According to the turret device 100, a pair of support parts 120 are alternately moved upward by a rotation of the swing tower 110. That is, by the rotation of the swing tower 110, one of the support portion 120 of the pair of support portions 120 and the ladle (L) supported by the support portion 120 are located above the tundish (T), at this time Another support 120 and a ladle L supported by the support 120 are positioned outside the tundish T.
[44]
Turret device 100 is not limited to the above-described embodiment, it is possible to apply a variety of configurations to support a pair of ladle (L), and alternately move them to the upper and standby positions of the tundish (T). .
[45]
The ladle (L), as shown in FIG. 2, forms an exterior, has an internal space to accommodate molten steel, and an opening through which the molten steel can be discharged (hereinafter, an outlet 321) and passage of gas The main opening 310 is provided with a possible opening (hereinafter, the inlet 322), and a top nozzle TN installed in the main body 310 so as to be able to communicate with the exit 321. In addition, it may further include a plug 330 that is inserted into the body 310 to be able to communicate with the inside of the body 310.
[46]
In an embodiment of the present invention, an 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 ingots and inclusions compared to the prior art. That is, by supplying molten steel to the ladle (L) or the tundish (T) supported on the support portion 120 positioned corresponding to the upper side of the tundish (T) among the pair of support portions 120 of the turret device 100 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 tundish (T). If this is described from the side of one ladle (L), when one tundish (T) is supported by the turret device 100 and is waiting outside of the tundish (T), the inert gas is injected into the ladle (L). After blowing, the ladle (L) moves upward to the tundish (T) to supply the molten steel to the tundish (T) (ie, participates in casting). The inert gas is blown into the ladle (L).
[47]
And, in the embodiment, in blowing the inert gas to the standby ladle (L), after the opening of the inlet 322 of the ladle (L) is injected with a relatively small amount of inert gas to reduce the occurrence of ingots or inclusions or Suppress. And, in blowing the inert gas to the ladle in the casting, after the ladle (L) is opened, when the casting is started, while reducing the flow rate of the inert gas in accordance with the molten steel height or the level of the hot water drop, reducing the occurrence of loosening and inclusions or Suppress.
[48]
To this end, a gas blowing device 200 is provided for injecting an inert gas into the waiting ladle L seated on the turret device 100 and the ladle L participating in casting, and controlling the gas blowing flow rate.
[49]
Referring to FIG. 3, the gas blowing device 200 includes a first blowing line 210a connectable with a ladle L supported at a standby position, and a second blowing line connectable with a ladle L supported at a casting position ( 210b), a first gas storage unit 220a providing high pressure inert gas and a second gas storage unit 220b providing low pressure inert gas, first and second gas storage units 220a, 220b and The first supply unit 230a, the first and the second supply units for supplying the inert gas of each of the first and second gas storage units 220a and 220b to the first injection line 210a by connecting one injection line 210a A second connecting the gas storage units 220a, 220b and the second blow line 210b to supply the inert gas of the first and second gas storage units 220a, 220b to the second blow line 210b. It includes a supply unit (230b).
[50]
Here, the first blowing line 210a is connectable to and detachable from the ladle (L) inlet 322 disposed in the standby position outside the tundish T, and the second blowing line 210b is the tundish T ) It can be connected and detached from the ladle (L) inlet 322 disposed in the upper casting position. In addition, each of the first and second blow lines 210a and 210b may be in the form of a pipe capable of moving inert gas.
[51]
In addition, the first blow valve 211a is installed on the extension path of the first blow line 210a, and the second blow valve 211b is installed on the extension path of the second blow line 210b.
[52]
The first supply unit 230a according to the embodiment has a first supply line 231a, one end of which is connected to the first gas storage unit 220a, one end of which is connected to the second gas storage unit 220b, and the other end of the second supply line The second supply line (234a) connected to the (210b), the first supply valve (232a) installed on the extended path of the first supply line (231a), the first flow control unit (233a), the second supply line (234a) It includes a second supply valve 235a and a second flow control unit 236a installed 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 positioned at the front end of the second supply valve 235a.
[53]
Each of the first and second supply lines 231a and 234a may be in the form of a pipe capable of moving inert gas.
[54]
The first supply valve 232a according to the embodiment may be, for example, a motor valve, the first flow control unit 233a at the rear end of the first supply valve 232a, and the second flow control unit 236a at the second supply valve It is preferably installed so as to be located at the rear end of (235b).
[55]
[56]
The second supply unit 230b according to the embodiment has a third supply line 231b, one end of which is connected to the first gas storage unit 220a, one end of which is connected to the second gas storage unit 220b, and the other end of the second supply line The fourth supply line 234b connected to the 210b, the third supply valve 232b installed on the extended path of the third supply line 231b, the third flow control section 233b, and the fourth supply line 234b It includes a fourth supply valve 235b and a fourth flow control unit 236b installed on the extended path. Here, the other end of the third supply line 231b may be connected to the fourth supply line 234b to be positioned at the front end of the fourth supply valve 235b.
[57]
Each of the third and fourth supply lines 231b and 234b may be in the form of a pipe capable of moving inert gas.
[58]
The third supply valve 232b according to the embodiment may be, for example, a motor valve, the third flow control unit 233b is at the rear end of the third supply valve 232b, and the fourth flow control unit 236b is the fourth supply valve It is preferably installed so as to be located at the rear end of (235b).
[59]
In the embodiment, by using the gas injection device 200 as described above, when the ladle (L) is in the atmosphere and the casting position in a state supported by the turret device, by blowing inert gas, for example, Ar gas, inclusions and sprinkles Reduce or suppress occurrence.
[60]
The gas blowing device 200 is not limited to the above-described configuration, and can be changed to various configurations capable of supplying an inert gas by adjusting pressure and flow rate to each of the first and second blowing lines 210a and 210b.
[61]
Hereinafter, with reference to FIGS. 3 to 5, a casting method including injecting an inert gas to each ladle L in an atmosphere and a casting position on a turret device using a gas blowing device 200 will be described. At this time, Ar gas will be described as an inert gas.
[62]
Casting method according to an embodiment of the present invention, the process of placing the ladle in which the molten steel is accommodated in each of the upper side of the tundish and the outside of the tundish, the molten steel of the ladle disposed at the casting position of the upper side of the tundish is supplied to the tundish, casting And a process of blowing an inert gas into a ladle disposed at a casting location.
[63]
Hereinafter, the casting method according to the embodiment will be described in more detail.
[64]
First, a ladle (L) in which molten steel is accommodated is supported on a pair of support portions 120 of the turret device 100. Among the pair of support parts 120, the ladle L positioned on the upper side of the tundish T participates in casting by supplying molten steel to the tundish T, and the other support part 120 is a tundish (T) Waiting for casting of the subsequent charge from the outside.
[65]
First, with reference to FIG. 4, a method of blowing an inert gas, such as Ar gas, into the standby ladle L will be described in detail.
[66]
In blowing Ar gas into the standby ladle, first, Ar gas is injected at a first flow rate for opening the ladle L. Here, the opening of the ladle L means that gas is supplied into the ladle through the main body 310 or plug 330 of the ladle L, and after the ladle L is opened, the gas injection flow rate is lowered. Even if it is possible to blow gas into the ladle (L).
[67]
The opening of the ladle L proceeds for a predetermined time from the start of gas injection, for example, may be within 10 seconds from the start of gas injection, and this section may be referred to as an initial injection section.
[68]
In the embodiment, in blowing the inert gas at a first flow rate into the standby 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), and the ladle (L ), The inlet 322 is opened.
[69]
And, when opening the ladle (L), or when injecting an inert gas at a first flow rate, the gas pressure is adjusted to more than 10 bar, 20 bar or less, and at a relatively high pressure compared to the pressure of the gas injected after opening It is desirable to be supplied.
[70]
On the other hand, for example, when the first flow rate is less than 80 LPM, the inlet 322 is not opened, so Ar gas may not flow into the ladle L. Conversely, when the flow rate of the inert gas at the initial stage of injection exceeds 200 LPM, the ladle (L) inlet 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 in that the area of ​​the occurrence of spun increases.
[71]
When the ladle (L) is opened, inert gas is blown at a second flow rate for reducing inclusions and spattering of molten steel, wherein the gas blowing flow rate is relatively small compared to the first flow rate at the time of opening the ladle (L).
[72]
In the embodiment, when the standby ladle (L) is opened, the gas is blown at a second flow rate of 1 LPM or more and 20 LMP or less, thereby reducing inclusions while finely bubbling molten steel and suppressing occurrence of sprinkling.
[73]
And, at this time, the pressure of the gas is supplied at a lower pressure than when opening the ladle (L). In the embodiment, the pressure is 2 bar or more and 10 bar or less.
[74]
On the other hand, when the second flow rate injected after the opening of the ladle L is less than 1 LPM, the effect of reducing inclusions due to inert gas bubbling may be low or may not be expressed. Conversely, when the second flow rate injected after opening the ladle L exceeds 10 LPM, there is no problem of suppressing the occurrence of sprinkling in the molten steel bath surface, or there is a problem in that the sprinkling area becomes large. In the case of a large surface area, inclusions are mixed into the molten steel through the surface area, thereby making it difficult to manufacture clean steel.
[75]
As described above, in blowing gas into the ladle L in the standby position, the gas blowing device 200 of FIG. 3 will be described below. First, in order to open the ladle L, in the state in which the second supply valve 235a is closed, when the first supply valve (for example, the motor valve) 232a and the first intake valve 211a are opened, the first gas storage unit Gas of (220a) is moved through the first supply line (231a), the second supply line (234a) and the first blow line (210a), it is blown into the inlet 322 of the ladle (L) in the standby position do. At this time, when the motor valve is opened, a gas having a high pressure of 10 bar or more and 20 bar or less instantaneously flows along the first supply line 231a. Let it flow. Therefore, the pressure is greater than 10 bar and less than or equal to 20 bar, and the Ar gas having a flow rate of 80 LPM or more and 200 LPM or less is blown into the standby ladle L to open the ladle L.
[76]
When the ladle L is opened, the first supply valve 232a is closed, and the operation of the first flow control unit 233a is stopped. Then, the second supply valve 235a is opened, and the second flow control unit 236a is operated to supply Ar gas at 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. By supplying to the line 234a and the first blow line 210a, Ar gas is blown into the standby ladle L. By blowing the Ar gas, molten steel in the standby ladle L is finely bubbled, and accordingly, inclusions in the molten steel in the standby ladle can be reduced, and generation of sprinkling can also be suppressed.
[77]
Thus, while bubbling molten steel in the ladle L in the standby position, the ladle L in the casting position continuously supplies molten steel to the tundish T to participate in casting.
[78]
Then, when the casting is finished at the casting position, the swing tower 110 of the turret device 100 is rotated, and the ladle being bubbled at the standby position as described above is moved to the upper side of the tundish T, that is, the standby position. Order.
[79]
Thereafter, the top nozzle TN of the ladle L and the shroud nozzle SN are mutually fastened, and the top nozzle TN and the shroud nozzle SN are communicated through the operation of the gate. Accordingly, molten steel in the ladle (L) is supplied to the tundish through the shroud nozzle (SN), and the nozzle of the tundish (T) (immersion nozzle 40) is transferred to the mold (M) and solidified in a predetermined shape. The cast is cast.
[80]
As such, when casting is performed by supplying molten steel in the ladle L positioned above the tundish T to the tundish T, the ladle L participating in the casting, that is, the ladle L placed at the casting position ) Ar gas is blown to bubble molten steel.
[81]
To this end, the second blow line 210b is connected to the blow hole of the ladle L moved to the casting position. Thereafter, Ar gas is supplied at a first flow rate for opening the ladle L. The opening of the ladle L proceeds for a predetermined time from the start of gas injection, for example, may be within 10 seconds from the start of gas injection.
[82]
In an embodiment, in blowing an inert gas at a first flow rate to the ladle L in the casting position, the first flow rate may be 80 LPM or more, 200 LMP or less (5 to 5 Nm 3 / h), through which the ladle ( The inlet 322 of L) is opened.
[83]
And, when blowing the gas at the first flow rate, the gas pressure is more than 10 bar, 20 bar or less, it is preferable to supply a relatively high pressure compared to the pressure of the gas blown after opening.
[84]
On the other hand, for example, when the first flow rate injected into the ladle L in the casting position is less than 80 LPM, the inlet 322 is not opened, and Ar gas may not be introduced into the ladle L. Conversely, when the first flow rate exceeds 200 LPM, the ladle (L) inlet 322 is opened, but causes the instability of the molten steel bath surface of the ladle (L), which may lead to operational instability, and the area where the spout occurs There is an increasing problem.
[85]
When the casting position ladle (L) is opened, an inert gas is blown in to reduce the occurrence of inclusions and spattering of molten steel. At this time, the gas injection flow rate is relatively small compared to the first flow rate at the time of opening the ladle (L).
[86]
In the embodiment, when the ladle L in the casting position is opened, the gas is blown at a lower flow rate than the blown flow rate at the time of opening, thereby reducing inclusions while finely bubbling molten steel and suppressing the occurrence of sprinkling.
[87]
And, at this time, the pressure of the gas is supplied at a lower pressure than when opening the ladle (L). In the embodiment, the pressure is 2 bar or more and 10 bar or less.
[88]
On the other hand, when the casting is performed by starting supply of molten steel in the ladle L of the casting position to the tundish T, since molten steel in the ladle L is continuously supplied to the tundish, the ladle L participating in the main My molten steel decreases in height with the lapse of casting time. Therefore, in the embodiment, in injecting the inert gas into the ladle L from the start of casting, the Ar gas blowing flow rate is varied according to the height of the molten steel in the ladle L or the height of the molten steel bath surface. In more detail, after the ladle L of the casting position is opened, when the molten steel in the ladle L starts to be supplied to the tundish, an inert gas is blown into the ladle. (m 0 ) '. And, in the embodiment, as the height of molten steel decreases as the casting proceeds, the gas is blown while decreasing to a lower flow rate (m 1 ) than the initial gas blowing flow rate (m 0 ) . That is, at the start of casting , based on the real-time current molten steel height or the current molten steel height (L 1 ) based on the molten steel height (hereinafter, the initial molten steel height (L 0 )), the flow rate is lower than the initial gas injection flow rate (m 0 ) (m Gas is blown with 1 ), which is represented by Equation 1 below when represented by a mathematical expression, and is represented by, for example, FIG. 5 when represented by a graph.
[89]
[Equation 1]
[90]

[91]
Here, the molten steel height (L 1 ) at the present time in the ladle can be calculated in real time through the molten steel height before discharging the molten steel, that is, the initial molten steel height (L 0 ) and the molten steel discharge speed. And, when starting to supply molten steel in the ladle in the casting position tundish, the initial gas injection flow rate (m 0 ) supplied to the ladle may be 1LPM or more, 20 LPM or less, and the pressure in the ladle (L) is 2 bar or more It is kept constant to 10 bar or less.
[92]
On the other hand, if the initial gas injection flow rate (m 0 ) exceeds 20 LPM, sprinkling may occur in molten steel in the ladle at the start of casting.
[93]
In addition, when the inert gas is blown at a constant flow rate regardless of the drop in the height of the molten steel during casting, there is no problem of inclusion reduction effect, the occurrence of sprinkling is not suppressed, or the problem that the sprinkling is largely generated. In other words, if the amount of molten steel in the ladle L, that is, the Ar gas is injected at a lower flow rate than the molten steel height L 1 at the present time , there is no effect of reducing inclusions due to the inert gas, and thus clean steel cannot be produced. Conversely, when the Ar gas is blown at a flow rate that is greater than the height of the molten steel (L 1 ) at the present time, the molten steel bath surface may be generated by a large amount of gas injected, or the surface area of ​​the molten metal may increase.
[94]
[95]
As described above, when injecting gas into the ladle L in the casting position, it will be described below using the gas injecting device 200 of FIG. 3.
[96]
First, in order to open the ladle L in the casting position, with the fourth supply valve 235b closed, when the third supply valve (for example, the motor valve) 232b and the second blow valve 211b are opened, the first The gas of the gas storage unit 220a moves through the third supply line 231b, the fourth supply line 234b, and the second blow line 210a, so that the inlet 322 of the ladle L in the casting position ). At this time, when the motor valve is opened, gas at a high pressure of 10 bar or more and 20 bar or less instantaneously flows along the third supply line 231b. Let it flow. Therefore, the pressure is greater than 10 bar and less than 20 bar to the ladle L of the casting position, and Ar gas having a flow rate of 80 LPM or more and 200 LPM or less is blown to open the ladle L.
[97]
When the ladle L is opened, the molten steel of the ladle L in the casting position starts to be supplied to the tundish T. At this time, the third supply valve 232b is closed, and the operation of the third flow control unit 233b is stopped. Then, the fourth supply valve 235b is opened, and the fourth flow control unit 236b is operated to supply Ar gas having a pressure of 2 bar or more and 10 bar or less and a flow rate of 20 LPM or less to the fourth supply line 234b. And supplied to the second blowing line 210b to blow Ar gas into the ladle L in the casting position.
[98]
At this time, the gas flow rate supplied to the ladle L is adjusted according to the change in the height of molten steel in the ladle L from the start of casting to the end of casting using the fourth flow control unit 236b. That is, as shown in Equation 1 and 5, the gas is blown while reducing the flow rate compared 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.
[99]
By blowing the Ar gas, molten steel in the standby ladle L is finely bubbled, and accordingly, inclusions in the molten steel in the standby ladle can be reduced, and generation of sprinkling can also be suppressed.
[100]
[101]
Hereinafter, with reference to FIGS. 6 and 7, the results of the molten steel treatment in the ladle using the comparative example and the molten steel treatment method according to the embodiment of the present invention will be described.
[102]
6 is a view showing the results of sprinkling when bubbling in a method according to a comparative example during ladle casting. In the case of the ladle shown in FIG. 6, one inlet is provided, and two outlets are provided. Accordingly, when the ladle shown in FIG. 6 is positioned corresponding to the upper side of the tundish, Ar gas is blown into one plug while discharging molten steel from the two outlets to the tundish. At this time, even if comparison of the examples, was supplied a predetermined amount of Ar gas, regardless of the molten steel height drop, Figure 6a is 10 Nm 3 / the h flow rate, Figure 6b is 5 Nm 3 as a result of blow-by / h flow rate, the slag It is a picture showing whether or not and how much sugar is generated through concentration.
[103]
Referring to Figures 6a and 6b, it can be seen that the separation between the slag of the molten steel bath surface is generated.
[104]
On the other hand, according to the embodiment of the present invention, in blowing the Ar gas to the ladle that is participating in the casting or in the casting position, the appropriate amount of Ar gas was blown according to the drop in the height of the molten steel. Thus, there was an effect that the generation of sprinkles was suppressed compared to the prior art.
[105]
[106]
7 is a graph showing the amount of inclusions in each operation step as an inclusion index. Here, the inclusion amount was calculated as the total amount of oxygen in the molten steel, and compared and shown.
[107]
7 is a graph showing an inclusion index in molten steel during molten steel treatment according to a method for treating molten steel according to Comparative Examples and Examples.
[108]
In the comparative example, the step of deoxidizing in a vacuum degassing facility, after deoxidation is finished, the Ar steel is blown into the ladle while the molten steel is heated up in the ladle furnace, bubbling, and the ladle containing the molten steel is held in the standby position of the turret device, waiting The ladle that was in progress was moved to the upper side of the tundish, and molten steel was supplied to the tundish to start casting. At this time, during the casting, the Ar gas was blown through the immersion nozzle, bubbling, and the molten steel in the tundish was supplied to the mold, and the inclusions in the molten steel in the mold were measured.
[109]
The embodiment is a step of deoxidizing in a vacuum degassing facility, after the deoxidation is finished, by blowing the Ar gas into the ladle while heating the molten steel in the ladle furnace, supporting the ladle containing the molten steel in the turret device, and then being in the standby position. When the ladle was blown with Ar gas into the ladle, the ladle in the standby position was placed above the tundish, and the molten steel was moved to the tundish to start casting. At this time, during the casting, the Ar gas was blown through the immersion nozzle, bubbling, and the molten steel in the tundish was supplied to the mold, and the inclusions in the molten steel in the mold were measured.
[110]
Among the operations according to these comparative examples and examples, the amount of inclusions in the molten steel was measured at each step. Of these, 'Tundish' in FIG. 7 is the amount of inclusions in molten steel in the tundish that does not perform separate bubbling.
[111]
And the amount of inclusions in each operation step was calculated as the total oxygen content in the molten steel. In addition, in calculating the inclusion index, it was calculated based on the amount of inclusions in molten steel in a vacuum degassing facility.
[112]
Referring to FIG. 7, it can be seen that in the case of the first to third embodiments, the inclusion index is decreased compared to the first and second comparative examples. More specifically, when the inclusion amount in the molten steel in the mold was compared, the inclusion amount in the example was reduced by 30% compared to the comparative example. That is, in the case of the comparative example and the example, in the case of bubbling during heating and immersion nozzle using the ladle furnace, in the case of the embodiment in which the ladle bubbling is performed in the atmosphere and during casting in the turret device, this is not performed. The inclusion is less than in the example. Therefore, when the casting method according to the embodiment is used, crack generation due to inclusions is less than that of the comparative example, that is, clean steel can be cast.
[113]
[114]
As described above, in the case of the casting method according to the embodiment of the present invention, the inert gas is blown in when the ladle L is in the standby position on the turret device 100 and during casting to supply molten steel to the tundish T do. Accordingly, inclusions can be reduced compared to the prior art, and clean steel can be produced. That is, when the ladle L is in the standby position, by performing fine bubbling, it is possible to reduce the occurrence of inclusions in the atmosphere. In addition, by injecting an inert gas into the ladle L during casting, it is possible to reduce inclusions in molten steel in the ladle L during casting.
[115]
In addition, as the flow rate of the gas is decreased as the height of the molten steel decreases during casting, it can be bubbled in an appropriate amount, and thus, it is possible to suppress or prevent the occurrence of spewing due to the inert gas. That is, when the gas is blown at an excessively large flow rate relative to the amount of molten steel or the height of the molten steel, slack may be generated in the slag of the bath surface due to vortex generation due to gas injection. L) By adjusting the gas injection flow rate to correspond to the decrease in the height of the molten steel, it is possible to suppress or prevent occurrence of spouting due to gas injection.
Industrial availability
[116]
According to the embodiment of the present invention, an inert gas is blown in when the ladle is in the standby position on the turret device and during casting to supply molten steel to the tundish. Accordingly, inclusions can be reduced compared to the prior art, and clean steel can be produced. That is, when the ladle is in the standby position, by initiating fine bubbling after opening the ladle, it is possible to reduce the occurrence of inclusions in the atmosphere. In addition, by injecting an inert gas into the ladle L during casting, it is possible to reduce inclusions in molten steel in the ladle during casting.
Claim
[Claim 1]
Positioning a ladle in which molten steel is accommodated in each of the upper side of the tundish and the outer side of the tundish; Supplying molten steel of a ladle disposed at a casting position above the tundish to the tundish to perform casting; And blowing an inert gas into the ladle disposed at the casting position. Casting method comprising a.
[Claim 2]
The method according to claim 1, The process of blowing the inert gas into the ladle disposed in the casting position, The process of blowing the inert gas at a first flow rate into the ladle disposed in the casting position, opening the ladle in the casting position; After the ladle of the casting position is opened, when casting to start supplying molten steel to the tundish is started, a process of blowing and bubbling an inert gas at a lower flow rate than the first flow rate; Casting method comprising a.
[Claim 3]
The method according to claim 2, In the bubbling of the ladle in the casting position, casting method for casting the inert gas injection flow rate decreases as the molten steel height in the ladle in the casting position.
[Claim 4]
The method according to claim 3, In reducing the flow rate of the inert gas in accordance with the drop of the molten steel in the ladle in the casting position , the current molten steel relative to the initial molten steel height (L 0 ) before supplying the molten steel in the casting position ladle to tundish Casting method for casting at a flow rate (m 1 ) calculated by Equation 1 using a ratio of height (L 1 ) and an initial gas injection flow rate (m 0 ) when supplying the treadmill to the casting position ladle . [Equation 1]
[Claim 5]
The method according to claim 4, wherein the initial gas injection flow rate (m 0 ) is 1 LPM or more and 20 LPM or less.
[Claim 6]
The method according to claim 1, Casting a casting method comprising the step of blowing an inert gas to the ladle disposed in the standby position outside the tundish.
[Claim 7]
The method of claim 6, wherein injecting an inert gas to the ladle disposed in the standby position comprises: injecting an inert gas at a first flow rate into the ladle disposed in the standby position to open the ladle in the standby position; After the ladle of the standby position is opened, when casting to supply molten steel to the tundish is started, a process of blowing and inert gas at a second flow rate lower than the first flow rate to bubble; Casting method comprising a
[Claim 8]
The method according to claim 7, wherein 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.
[Claim 9]
A tundish that temporarily stores molten steel; A turret device having a pair of support portions for supporting a pair of ladles in which molten steel is accommodated, and alternately positioning the pair of support portions in a casting position above the tundish and an atmospheric position outside the tundish. ; A mold positioned below the tundish to solidify molten steel provided from the tundish; A gas blowing device connectable 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 in the standby position and the ladle supported in the casting position on the turret device; Foundry equipment comprising a.
[Claim 10]
The method according to claim 9, The gas blowing device, A first blowing line connectable with a ladle supported in the standby position; A second blow line connectable with a ladle supported at the casting position; And a first supply part connected to the first blow line to selectively supply an inert gas to the first blow line at a first flow rate for opening the ladle in the standby position and at a second flow rate smaller than the first flow rate. ; A second supply part connected to the second blow line to selectively supply an inert gas to the second blow line at a first flow rate for opening the ladle in the casting position and at a smaller flow rate than the first flow rate; Foundry equipment comprising a.
[Claim 11]
The method according to claim 10, The first supply unit, to supply the inert gas at a first flow rate of 80 LPM or more, 200 LPM or less to the first blow line, so that the inlet of the ladle in the standby position is opened, the standby position After the ladle is opened, a casting facility for bubbling the ladle in the atmospheric position by supplying an inert gas at a second flow rate of 1 LPM or more and 20 LPM or less to the first blow line.
[Claim 12]
The method according to claim 10, The second supply unit, to supply an inert gas at a first flow rate of 80 LPM or more, 200 LPM or less to the second blow line, so that the inlet of the ladle in the casting position is opened, the casting position After the ladle of the hole is opened, when molten steel in the ladle at the casting position begins to be supplied to the tundish, the height of molten steel in the ladle at the casting position is lowered in the flow rate range lower than the first flow rate to the second blow line. Casting method for reducing the inert gas blowing flow according to.