KR20020051088A - Molten metal supply method and equipment for continuous casting - Google Patents

Abstract

PURPOSE: An apparatus and a method for supplying molten metal for continuous casting are provided to improve surface and internal quality of final products by controlling a supplying speed of molten metal during continuous casting of steel or other metals. CONSTITUTION: In an apparatus for supplying molten metal for continuous casting in which the molten metal(14) is supplied to a mold(20) forming ingot after temporarily storing the molten metal by receiving molten metal(14) supplied from a ladle(10) for continuous casting of steel or metal, the apparatus comprises a tundish(16) which stores the molten metal by receiving molten metal(14) supplied from the ladle(10), and which is installed at the side direction of the mold(20) so that a surface level of the received molten metal is higher than a module of the surface of the molten metal of the mold; and a connection unit for supplying molten metal received in the tundish(16) to the mold(20) by a difference between the surface level of molten metal in the tundish and the surface level of molten metal in the mold(20), wherein the connection unit is integrally equipped with an inflow part(24), a connection part(26) and a submerged nozzle part(28), a molten metal supply port(30) is formed on the connection part(26) while a sliding gate valve(32) is equipped at the submerged nozzle part(28), and the apparatus further comprises a support unit(18) vertically reciprocating the tundish to control the surface level of molten metal in the tundish.

Description

Molten metal supply method and equipment for continuous casting

The present invention relates to a molten metal supply device for continuous casting, and more particularly, a connection between the tundish and the mold of the instrument by a sealed communication device, and the molten metal filled in the communication device, and between the tundish and the mold By the siphon effect generated by the level difference of molten metal, molten metal is supplied to the mold through the communication device, and the amount of molten metal supplied to the mold can be controlled by adjusting the level of molten metal between the tundish and the mold. Molten metal supply apparatus for continuous casting and a supply method thereof.

In general, steel continuous casting method has been widely used all over the world since the 1960s, and has many advantages over the previous ingot method, and produces more than 60% of the world's crude steel using continuous casting. Japan, Korea In major iron producing countries such as Western Europe, more than 90% of the steel is manufactured using the continuous casting method.

Typically, the machine used in the continuous casting process is a ladle 2 for supplying the molten metal 1, and a tundish 4 for receiving molten metal from its outlet 3 at the bottom of the ladle 2; Is arranged. In the lower part of the tundish 4, a mold 6 is provided which receives molten metal by the deposition nozzle 5 and actually casts a continuous casting such as slab. Of course, the immersion nozzle 5 is provided with a sliding gate 7 to control the amount or supply direction of the molten metal supplied to the mold 6 through the immersion nozzle (5). In addition, a stopper rod 8 for adjusting the opening degree of the deposition nozzle 5 is provided at the tundish.

Looking at the supply of molten metal in the machine configured as described above, the molten metal is supplied to the inside of the mold (6) through the immersion nozzle (5) attached to the lower portion of the tundish (4) located directly above the mold (6) Done. At this time, the level difference (L) of the molten metal between the tundish 4 and the mold 6 located directly above the mold 6 reaches about 1.5 m or more, and the free fall speed due to gravity is about 5.4. Flow rate of molten metal is very fast, above m / s, by adjusting opening degree by sliding gate 7 and / or stopper rod 8 between tundish 4 and mold 6 Control the flow rate by reducing the speed. Typically, when casting steel, the thickness of the cast steel is 230 ~ 250mm, the width is about 1 ~ 1.6m, the cross section of the immersion nozzle discharge port is about 80 x 70 ㎜, the cross-sectional area ratio is about 20 to 40 times, the nozzle The molten metal discharge rate at the outlet is 20 to 40 times the casting speed. In this way, as the molten metal flows into the mold 6 in a state where the flow rate of the molten metal is greatly different, the flow of the molten metal in the mold 6 becomes extremely unstable. As a result, fluctuations in the mold surface or free surface of the mold become severe, drift occurs, and liquid or solid mold powder is mixed into the mold, and various non-metallic inclusions contained in the molten metal are injured on the surface of the mold. There is a problem that can be mixed into the mold without causing a serious obstacle to product quality.

On the other hand, in order to solve such a problem and to improve the quality of the cast steel, a technique for improving the quality of the cast steel is mainly used by appropriately changing the discharge angle of the deposition nozzle. The discharge angle of the deposition nozzle has a great influence on the molten metal flow. In other words, as the discharge downward angle becomes larger, the amount of downflow increases and the amount of upflow decreases, so that the molten metal flow rate is relatively reduced in the molten metal's molten metal to maintain a stable molten surface. While the surface quality of cast steel is improved by solidification, relatively large amount of non-metallic inclusions and bubbles penetrate deeply into the mold together with the downflow, so that it does not float on the surface of the cast steel, so it solidifies with the metal inside the cast steel. Therefore, there is a problem of deteriorating the internal quality of the cast steel. On the other hand, if the discharge downward angle is reduced, inclusions and bubble defects are reduced as the amount of downflow decreases, while the amount of upflow increases and the rate of molten metal in the water surface increases rapidly. There is a problem that the surface quality deteriorates due to the formation of vortex. Such a problem is a problem that has emerged more seriously as the casting speed has recently been increased.

As described above, there is a limit to the control of the molten metal flow using only the deposition nozzle, and there are proposals to solve this problem, such as Swedish Patent No. 8003695, US Patent No. 4,495,984, and the like. According to these patents, there has been proposed an apparatus for providing a direct current magnetic field at a local part directly below the discharge port of the immersion nozzle and reducing the flow rate of the molten metal after discharge of the immersion nozzle using the Lorentz force caused by the magnetic field and the flow. Although these devices were actually applied in steel mills, they have not been used recently because of the problem of flow distortion in the direction of avoiding the flow resistance caused by the magnetic field, rather than the effect of the flow decelerating by the magnetic field installed at the local site.

On the other hand, as a proposal to solve the above-mentioned problems are Swedish Patent No. 9100184, US Patent No. 5,404,933, Japanese Patent Laid-Open No. 2-284750. These patents disclose a method of horizontally distributing a magnetic field over the full width of the mold. However, it still fails to fundamentally solve the problems as described above because it does not fundamentally slow down the discharge speed of the deposition nozzle.

In practice, at the same flow rate, the flow velocity is inversely proportional to the flow cross-sectional area, so if the cross-sectional area of the deposition nozzle can be increased, the discharge rate can be reduced, but the cross-sectional area of the upper part of the deposition nozzle, i.e., the connection with the tundish remains the same as before. Increasing the cross-sectional area near the outlet of the immersion nozzle only causes the flow separation to occur inside the nozzle, so that the flow becomes extremely uneven. Therefore, the cross-sectional area of the nozzle top must be increased at the same time. However, in this case, it is very difficult to control the flow rate or the supply amount of the molten metal by adjusting the opening degree of the deposition nozzle by the stopper rod or the sliding gate valve.

As a result, in order to fundamentally solve the problems described above, it has been shown that the discharge speed of the molten metal must be slowed down inside and outside the deposition nozzle.

Accordingly, the present invention has been invented to solve the problems and problems described above, the object of the present invention is to adjust the feed rate of the molten metal during continuous casting of steel or other metals to improve the quality of the surface and internal quality of the final product It is to provide a molten metal supply apparatus and method for continuous casting that can be improved.

It is another object of the present invention to provide a molten metal supply apparatus and a method for smoothing a supply rate of molten metal supplied from a tundish to a mold.

Another object of the present invention is to provide a molten metal supply apparatus and method for continuous casting which can improve productivity by supplying a large amount of molten metal into a mold while gently injecting molten metal into the mold.

1 is a cross-sectional view showing a molten metal supply process during conventional continuous casting;

2 is a cross-sectional view showing a molten metal supply apparatus according to a first embodiment of the present invention;

3 is a cross-sectional view showing a molten metal supply apparatus according to a second embodiment of the present invention;

4a to 4b are cross-sectional views showing the initial application of the molten metal supply device of FIG.

♣ Explanation of symbols for the main parts of the drawing ♣

10 ladle 14 molten metal

18: support device 20: mold

22, 42: communication device 24, 44: inlet

26, 46: connection part 28, 48: immersion nozzle part

30: molten metal supply port 32, 50: sliding gate valve

In the molten metal supply apparatus for continuous casting for supplying the molten metal to the mold to form the ingot after receiving and temporarily storing the molten metal supplied from the ladle for continuous casting of steel or metal, the ladle A tundish for receiving and storing molten metal supplied from the molten metal and having a molten metal level higher than that of the molten metal of the mold; And a communication device for supplying the molten metal of the tundish to the mold by the difference between the level of the molten metal of the tundish and the level of the molten metal of the mold. By a molten molten metal feeder.

In addition, the method according to the present invention comprises the steps of closing the sliding gate provided in the deposition nozzle portion of the communication device, receiving molten metal from the ladle to fill the tundish and communication device to initialize; Supplying molten metal into the mold by opening the sliding gate valve of the deposition nozzle part when the communicating device is completely filled with molten metal; Performing continuous casting by moving the dummy bar when the molten metal supplied into the mold is filled to a desired level; And controlling the supply amount of the molten metal by adjusting a level difference between the level of the molten metal of the tundish and the level of the molten metal of the mold. .

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

First, referring to FIG. 2, the molten metal supply device for continuous casting according to the first exemplary embodiment of the present invention basically accommodates and stores molten metal 14 supplied from the outlet 12 of the ladle 10. A tundish 16 having a constant volume is provided. In particular, the tundish 16 is preferably installed to be moved up and down by the support device 18 shown in dashed lines. Optionally, the tundish 16 does not have a deposition nozzle at its bottom, unlike conventional tundishes.

In particular, the melt rapid supply device according to the present invention includes a communication device 22 for supplying molten metal in the tundish 16 to the mold 20. The communication device 22 is generally vertically disposed upwardly from the inside of the tundish 16 and an inlet portion 24 for introducing molten metal, and a connecting portion bent at the inlet portion 24 and extending substantially horizontally. (26) and the discharge part or the immersion nozzle part 28 integrally bent from the connection part and extended below the mold 20.

In addition, it is preferable that a separate molten metal supply port 30 for initially supplying molten metal to the mold is provided at the position of the connecting portion 26 of the communication device 22.

In addition, the immersion nozzle portion 28 is preferably provided with a sliding gate 32 to control the amount of molten metal supplied to the mold 20 through the immersion nozzle portion.

In particular, according to the molten metal supply apparatus according to the present invention, the mold 20 is disposed on the side of the tundish 16, and the free surface of the molten metal of the tundish 16, that is, the level L1 of the molten metal. It is preferable that the free surface of the molten metal of this mold 20, i.e., be kept higher than the level L2 of the molten metal.

On the other hand, referring to Figure 3, the molten metal supply apparatus according to the second embodiment of the present invention is basically a certain volume to receive and store the molten metal 14 supplied from the outlet 12 of the ladle 10 It has the tundish 40 which has. In particular, the tundish 40 is preferably installed to be moved up and down by the support device 18 shown in dashed lines. Optionally, the tundish 40 does not have an immersion nozzle installed at its bottom, unlike the conventional tundish.

In particular, the tundish 40 of the molten metal supply device according to the present invention includes a communication device 42 for supplying the molten metal to the mold 18 integrally. The communication device 42 forms a space for introducing the molten metal together with one side wall 40a of the tundish 40 and is formed to be bent at the inlet portion 44 and the inlet portion constituting the upright portion. The connecting portion 46 generally extends horizontally, and the discharge portion or the immersion nozzle portion 48 which is bent from the connecting portion and extends upwardly of the mold 18. Optionally, as described below in detail, the connection portion 46 is preferably provided with a relief valve 47 for discharging the air in the communication device 42 to the outside during the initial molten metal injection.

In addition, the immersion nozzle portion 48 of the communication device 42 is preferably provided with a sliding gate valve 50 to control the amount of molten metal supplied to the mold 18 through the immersion nozzle portion.

In particular, according to the molten metal supply apparatus according to the second embodiment of the present invention, the mold 18 is disposed on the side of the tundish 40, and the free surface of the molten metal of the tundish 40, that is, the molten metal It is preferable that the level L1 is maintained higher than the free surface of the molten metal of the mold 18, that is, the level L2 of the molten metal.

As a result, according to the molten metal supply apparatus for continuous casting according to the present invention, the flow rate of the molten metal 14 supplied into the mold 18 of the continuous casting machine, the mold 18 and tundish (16; 40) By controlling by using the level difference L between the surfaces, the molten metal 14 can be injected into the mold 18 at a relatively slow speed while supplying the same flow rate of molten metal to the mold as in the conventional casting method. And it is possible to manufacture a cast (metal ingot) excellent in internal quality. In addition, by using such a molten metal supply device, the molten metal 14 can be injected into the mold 18 at the same or lower speed while supplying a large amount of molten metal as compared with a conventional casting method. Will be.

In addition, the tundish (16; 40) is disposed on the side rather than the upper portion of the mold 20, and connected between the mold 18 and the tundish (16; 40) by a sealed communication device (22; 42), respectively The flow rate of the molten metal can be controlled by adjusting the siphon effect caused by the difference L of the molten metal level (L) accommodated in the molten metal and the difference (L) of the molten metal level between the tundish 16 and the mold 18. It is.

Accordingly, the cross-sectional area of the immersion nozzle can be increased without disturbing the flow in the immersion nozzle portions 28 and 48, so that the flow rate of the molten metal 14 is relatively slow while supplying the same flow rate as in the conventional casting method. Can be injected into the mold 20, and the molten metal 14 can be injected into the continuous casting mold 20 at the same or lower speed while supplying a higher flow rate than the conventional casting method. do. The level difference L of the molten metal between the tundish 16 and 40 and the mold 20 controls the flow rate of the molten metal supplied from the first ladle 10 to the tundish 16 and 40 to determine the tundish. It is controlled by two main methods: a method of changing the level of molten metal (L1) at (16; 40), and a method of moving the whole tundish (16; 40) up and down using the second support (18). Can be.

As described above, in the flow rate control means according to the present invention, the level difference, that is, the level difference L between the tundish and the mold required to supply the predetermined flow rate at the required speed can be calculated as follows. The flow energy equation between the tundish level surface L1 and the mold level surface L2 through the devices 22 and 42 is given by the following equation (1).

....... Formula (1)

Where P is pressure, z is height, V is flow velocity, rho is density, g is gravitational acceleration, h sub A is energy applied to system, h sub L is loss energy, and subscripts t and m are tundish, respectively And the template.

In Equation (1), since no energy h sub A is applied to the system, h sub A = 0, the tundish pressure P sub t and the mold pressure P subm are equal to each other as atmospheric pressure, and V sub t and V sub m are negligible, assuming that the level remains constant at the speed of movement of the free surface of the tundish and the mold, respectively.

Therefore, Equation (1) can be summarized as Equation (2) below.

z sub t-z sub m ~ = ~ h sub L ....... Equation (2)

That is, the level difference required to supply a predetermined flow rate at the required speed, that is, the level difference between tundish and the mold (L: z sub t-z sub m) is a loss in the molten metal communication device (22; 42). It is equal to the energy h sub L.

In addition, the loss energy (h sub L) in the molten metal communication device (22; 42) is composed of a pipeline friction loss (major loss) (h sub 1) and a minor loss (h sub 2). It is calculated as Equation (3) (4) (5).

h sub L ~ = ~ h sub 1 + h sub 2 Expression (3)

Formula (4)

Formula (5)

Where f is the coefficient of friction, Is the sum of the loss coefficients, L is the length of the pipeline, d is the diameter of the pipeline, and V is the average velocity in the pipeline.

Accordingly, the pipe friction loss (h sub 1) is determined by the hydraulic diameter and length of the passage and the roughness inside the pipe, and the secondary loss (h sub 2) is the shape of the pipe inlet and outlet and the shape of the pipe. It depends on the presence, extension, reduction, branching, and bends.

As an example of the practical calculation, a simple molten metal supply device composed of a passage having a uniform cross section having two sections where the communication device 22 is bent at a right angle as shown in FIG. In continuous casting, about 2.8 tons of molten metal per minute is supplied into the mold through a deposition nozzle of about 80 mm in diameter, with an average flow velocity of about 1.2 m / s and an average roughness within the deposition nozzle. 0.2 mm or less.

In this state, when the internal cross-sectional area of the deposition nozzle 28 is doubled by the method according to the present invention, the average flow velocity in the deposition nozzle can be reduced to about 0.6 m / s, and the required tundish The level difference L between the molds can be calculated as follows.

i) calculation of pipeline friction loss (h sub 1);

Reynolds Number = = = 37,333 >>2,300; (Turbulent zone)

Relative illumination ) = = 0.00357

In the Moody Chart, the coefficient of friction (f) is about 0.028, so Equation (4)

= 0.028 = 0.01378 m

Is calculated.

ii) calculating the subloss (h sub 2);

Loss factor at sharp inlet, K sub 1 0.5

Loss factor at exit, K sub 2 1.0

90 sup o Loss factor at bends, K sub 3 As 0.4,

= 0.5 + 1.0 + 0.8 = 2.3, so in equation (5)

= 2.3 = 0.0422 m,

Thus, lost energy = 0.056 m.

As a result, the level difference L between the tundish and the mold may be about 56 mm.

The arrangement and flow control method of the molten metal passageway and tundish and mold disclosed in the embodiments according to the present invention are just one embodiment, and various modifications and modifications can be made by those skilled in the art without departing from the scope of the present invention. An example would be possible.

Hereinafter, a practical embodiment for implementing the present invention will be described.

Example 1.

As shown in FIG. 2, the tundish 16 is positioned on the side of the mold 20, not directly above it, and the mold 22 and the tundish 16 are connected by a sealed molten metal communication device 22. As shown in FIG. Through the communication device 22 by a siphon effect generated by the molten metal 14 filling the interior of the communication device and the molten metal level difference L between the tundish 16 and the mold 20. The molten metal 14 is supplied. Initially, the casting start time is supplied to the molten metal 14 through a separate molten metal supply port 30 to fill the interior of the communication device 22. While maintaining the level L2 of the molten metal of the mold 20 during the casting operation, the amount of molten metal supplied from the ladle 20 to the tundish 16 is adjusted to adjust the tundish molten metal level L1 up and down. By controlling the molten metal level difference L between the tundish 16 and the mold 20, the flow rate of the molten metal supplied to the mold M is controlled.

Example 2.

As shown in FIG. 2, the tundish 16 is positioned on the side of the mold 20, not directly above the mold 20, and the communication device 22 is connected between the mold 20 and the tundish 16 by a sealed communication device 22. Molten metal 14 through the communication device 22 by the siphon effect generated by the molten metal 14 filling the inside and the molten metal level difference L between the tundish 16 and the mold 20. To supply. At the beginning of casting, the molten metal is supplied through a separate molten metal supply port 30 to fill the inside of the molten metal communication device 22. The molten metal level between the tundish 16 and the mold 20 is moved by moving the whole tundish 16 mechanically up and down using the support 18 while maintaining the level L2 of the mold hot water surface during the casting operation. By varying the difference L, the flow rate of the molten metal supplied to the mold is controlled.

Example 3.

As shown in FIG. 3, the tundish 40 is positioned on the side of the mold 20 rather than directly, and a portion between the mold 20 and the tundish 40 is formed together with a portion of the tundish 40. The communication device by the siphon effect generated by the molten metal 14 which is connected to the hermetic communication device 42 to fill this communication device and the molten metal level difference L between the tundish 40 and the mold 20. The molten metal 14 is supplied via 42.

On the other hand, the initialization operation of the molten metal supply device configured as described above will be described in detail with reference to Figures 4a to 4d.

First, as shown in FIG. 4A, the molten metal is supplied from the ladle to start filling the tundish 40 while the sliding gate 50 provided in the deposition nozzle portion 48 of the communication device 42 is closed. .

At this time, as shown in Figure 4b, while the air inside the molten metal communication device 42 is naturally removed through a relief valve 47 that may be provided in the connection portion 46 of the communication device 42, The molten metal is filled in the communication device 42.

Then, when the molten metal is completely filled in the communication device 42, the relief valve 47 is closed, and as shown in FIG. 4C, the sliding gate valve 50 of the deposition nozzle portion 48 is opened to the molten metal into the mold 20. Start supplying 14.

Subsequently, when the molten metal 14 is filled to the desired level in the mold 20 in the same manner as in the general continuous casting initiation method, as shown in Fig. 4D, the dummy bar 52 is moved to continue casting. During the casting operation, while maintaining the level (L2) of the molten metal of the mold, the amount of molten metal supplied from the ladle to the tundish 40 is adjusted to adjust the level L2 of the tundish up or down or the tundish 40 By moving the whole mechanically up and down, the flow rate of the molten metal supplied to the mold 20 can be controlled by controlling the level difference L of the molten metal between the tundish 40 and the mold 20.

Thus, the rate of molten metal fed from the tundish to the mold can be kept gentle while the supply amount can be increased.

As a result, according to the molten metal supply apparatus for continuous casting according to the present invention, when the molten metal is supplied from the tundish to the mold, the discharge rate from the deposition nozzle is reduced to stabilize the mold hot water surface and the floating separation ability of bubbles or non-metallic inclusions is improved. This improves the surface quality and the internal quality of the cast steel.

In addition, while the supply speed of the molten metal is a low speed while the supply amount is a large amount, the casting speed and the amount can be increased without deterioration of quality, thereby improving productivity.

While a preferred embodiment according to the present invention has been described above, it will be understood by those skilled in the art that various modifications and changes can be made without departing from the scope of the appended claims.

Claims (6)

In the continuous casting molten metal supply device for continuous casting of steel or metal, the molten metal supplied from the ladle is temporarily stored after receiving the molten metal from the ladle to supply the molten metal to the mold to form the ingot, A tundish for receiving and storing molten metal supplied from the ladle and having a molten metal level higher than that of the molten metal of the mold; And And a communication device for supplying the molten metal of the tundish to the mold by the difference between the molten metal contained in the tundish and the level of the hot surface of the tundish. Molten Metal Feeder. According to claim 1, wherein the communication device is an inlet for injecting the molten metal of the tundish, the connecting portion is bent in the inlet to extend horizontally, the immersion nozzle is bent from the connecting portion extending above the mold Continuous casting molten metal supply apparatus characterized in that it comprises a unit integrally. According to claim 1, wherein the communication device is the inlet is introduced into the molten metal of the tundish and formed with one side wall of the tundish, the inlet is formed to be horizontally extended and the air is charged during the initial molten metal filling A molten metal supply device for continuous casting, comprising: a connecting portion having a relief valve for discharging; and a deposition nozzle portion bent from the connecting portion and extending upward of the mold. The molten metal supply port of claim 2, wherein the connection part is provided with a molten metal supply port for filling molten metal, and the deposition nozzle part is provided with a sliding gate valve for controlling a flow rate of molten metal supplied to the mold. Continuous casting molten metal supply apparatus, characterized in that. The molten metal supply device for continuous casting according to claim 1, further comprising a support device capable of reciprocating the tundish up and down to adjust the level of the hot water surface of the tundish. In the molten metal supply method using a molten metal supply apparatus according to any one of claims 1 to 5, Closing the sliding gate provided in the immersion nozzle portion of the communication device, receiving molten metal from the ladle, and filling and filling the tundish and communication device; Supplying molten metal into the mold by opening the sliding gate valve of the deposition nozzle part when the communicating device is completely filled with molten metal; Performing continuous casting by moving the dummy bar when the molten metal supplied into the mold is filled to a desired level; And And controlling the supply amount of the molten metal by adjusting a level difference between the level of the molten metal of the tundish and the level of the molten metal of the mold.