KR20240141279A - Immersion nozzle - Google Patents

Abstract

An immersion nozzle having an internal barrier, a branch flow path, and a distribution block, wherein when one of the branch flow paths is blocked, the relationship between the flow rate Qa of molten steel discharged from an inner discharge hole arranged in an area where the branch flow path is blocked and the flow rate Qb of molten steel discharged from an inner discharge hole arranged in an area where the branch flow path is not blocked satisfies equation (1), and the relationship between the flow rate Q _out of molten steel discharged from an outer discharge hole and the flow rate Q _IN of molten steel discharged from the inner discharge hole satisfies equation (2). Qa/Qb>1.0 … (1), 0.1≤Q _IN /Q _out ≤1.0 … (2)

Description

Immersion nozzle

The present invention relates to an immersion nozzle used for feeding molten steel from a tundish to a mold in continuous casting of molten steel.

The present invention relates to an immersion nozzle that disperses and supplies a discharge flow into a mold, particularly in high-speed casting.

This application claims priority from Japanese patent application No. 2022-047181, filed on March 23, 2022, the contents of which are incorporated herein.

In an immersion nozzle used for feeding molten metal from a tundish to a mold, high-speed casting conditions in which the casting speed exceeds 3 m/min and reaches a maximum of 5 to 8 m/min are used in thin-slab continuous casting, etc.

When such high-speed casting conditions are applied, it is required to pour the molten steel into the mold downward along the vertical direction from the viewpoint of preventing disturbance of the melt surface within the mold.

In addition, from the perspective of dissipating the kinetic energy of the discharged flow within the mold (in other words, reducing the discharge flow rate), it is required to expand the discharge hole area by making the discharge hole porous or the like.

According to these requirements, immersion nozzles of various shapes have been proposed in the past.

For example, as disclosed in Patent Documents 1 to 4, a multi-porous nozzle is proposed in which four or more discharge holes are arranged at the bottom of an immersion nozzle.

Alternatively, as disclosed in Patent Documents 5 to 7, research is known to reduce the flow rate of the downward flow inside the immersion nozzle by providing a barrier inside, or to smoothly distribute the downward flow to a plurality of discharge holes.

Japanese Patent Publication No. 2004-514562 Japanese Patent Publication No. 8-39208 Japanese Patent No. 3186068 Japanese Patent No. 4580135 Japanese Patent No. 4542631 Japanese Patent No. 3408884 Japanese Patent No. 6666908

The inventors conducted a study using a water model experiment.

As a result, it was found that the prior art had the following problems.

In the downward flow inside the immersion nozzle, unstable fluctuations (flow bias or fluctuations in the bias state) occur due to the influence of flow restriction mechanisms such as stoppers or slide gates that control the amount of hot water supplied from the tundish to the immersion nozzle.

The distribution of flow to the multi-hole discharge holes changes due to the influence of the downflow fluctuations.

As a result, the flow within the mold fluctuates unstably (i.e., left-right drift or state fluctuations occur).

If this happens, there is a risk of defects occurring on the surface of the slab being manufactured.

To stabilize the flow rate distribution to the multi-hole discharge holes, the discharge hole area can be reduced to increase the pressure inside the immersion nozzle.

However, doing so will damage the original purpose of porosity, which is to reduce the discharge flow rate.

In this way, it was a problem of the prior art that it was difficult to achieve both distribution of the flow rate to the multi-hole discharge holes and reduction of the discharge flow rate.

The present disclosure was made to overcome such technical challenges, and aims to provide an immersed nozzle capable of suppressing uneven flow of molten steel within a mold by adding a self-stabilizing function to the distribution of discharged flow through a study of the internal structure of the immersed nozzle.

The gist of this disclosure is as follows.

(1) The first aspect of the present invention is an immersion nozzle for continuously casting a slab by discharging molten steel supplied from a tundish into a mold, wherein the immersion nozzle has a discharge portion that supplies the molten steel to the mold, the immersion nozzle has two regions divided by a thickness-directed plane passing through an axis center, the discharge portion has a bottom portion and a side wall extending in a height direction from an outer edge of the bottom portion, four discharge holes are formed in the discharge portion, two of the discharge holes are arranged side by side in the width direction in each of the regions in the bottom portion of the discharge portion, the discharge portion is arranged at the center in the width direction, an internal barrier that distributes the molten steel supplied from the tundish to each of the regions, a branch flow path in which a branch flow of the molten steel distributed by the internal barrier flows between the side wall and the internal barrier of each of the regions, and the molten steel passing through the branch flow path is on the bottom side relative to the internal barrier in each of the regions. By further distributing the branch flow into the distribution flow path, and having a distribution block which supplies the branch flow to each of the discharge holes, and among the two discharge holes arranged in each of the above areas, the discharge hole arranged on the outer side in the width direction is an outer discharge hole, and the discharge hole arranged on the inner side in the width direction is an inner discharge hole, and when one of the branch flow paths is closed, the relationship between the flow rate Qa of the molten steel discharged from the inner discharge hole arranged in the area where the branch flow path is closed and the flow rate Qb of the molten steel discharged from the inner discharge hole arranged in the area where the branch flow path is not closed satisfies equation (1), and the relationship between the discharge flow rate Q _out of the molten steel discharged from the outer discharge hole and the discharge flow rate Q _IN of the molten steel discharged from the inner discharge hole satisfies equation (2).

Qa/Qb>1.0 … (1)

0.1≤Q _IN /Q _out ≤1.0 … (2)

(2) In the immersion nozzle described in (1) above, the immersion nozzle has a direct driving part for receiving the molten steel supplied from the tundish, the discharge part, and a connection part for connecting the direct driving part and the discharge part, and when the immersion nozzle is projected onto a horizontal plane, the projected area of the internal barrier may be greater than or equal to the flow path area of the direct driving part.

(3) In the immersion nozzle described in (1) or (2) above, the surface of the inner barrier that receives the molten steel supplied from the tundish may have a concave portion.

(4) In the immersion nozzle described in any one of the above (1) to (3), in each of the above regions, the outer discharge angle α1 defined from the angle of the wall surface forming the outer discharge hole may be between 40° downward and 75° downward, and further, the relationship with the inner discharge angle α2 defined from the angle of the wall surface forming the inner discharge hole may satisfy equation (3).

-5°≤|α2|-|α1|≤15° … (3)

(5) In the immersion nozzle described in any one of the above (2) to (4), the value of the flow path area of the branch flow path/the flow path area of the direct driving part may be 0.4 or more and 1.5 or less.

(6) In the immersion nozzle described in any one of the above (2) to (5), the value of the flow path area of the distribution flow path/the flow path area of the direct driving part may be 0.3 or more and 1.5 or less.

According to the immersion nozzle of the present disclosure, uneven flow of molten steel within a mold can be suppressed.

Figure 1 is a schematic diagram of a typical slab continuous casting device.
Figure 2 is a schematic diagram showing the state in which an imbalance occurs in the flow of molten steel within a mold.
Figure 3 is a cross-sectional view in the width direction passing through the axial center C of the immersion nozzle (100).
Figure 4 is a plan view of an immersion nozzle (100).
Figure 5 is a bottom view of the immersion nozzle (100).
Figure 6 is a projection drawing of the immersion nozzle (100) projected onto a horizontal plane, and is a drawing that focuses on the flow path (11) and the internal barrier (34).
Figure 7 is an enlarged view of the inner barrier (34).
Figure 8 is an enlarged view of the bottom (31) side of the discharge portion (30).
Figure 9 is a cross-sectional view in the width direction passing through the axial center C of the immersion nozzle (200).
Figure 10 is an enlarged view of the bottom (131) side of the discharge portion (130).
Figure 11a is a schematic diagram showing the state of the discharge portion of the immersion nozzle of Experimental Example A.
Figure 11b is a schematic diagram showing the state of the discharge portion of the immersion nozzle of Experimental Example B.
Figure 11c is a schematic diagram showing the state of the discharge portion of the immersion nozzle of Experimental Example C.
Figure 11d is a schematic diagram showing the state of the discharge portion of the immersion nozzle of Experimental Example D.
Figure 11e is a schematic diagram showing the state of the discharge portion of the immersion nozzle of Experimental Example E.
Figure 11f is a schematic diagram showing the state of the discharge portion of the immersion nozzle of Experimental Example F.
Figure 11g is a schematic diagram showing the state of the discharge portion of the immersion nozzle of Experimental Example G.
Figure 11h is a schematic diagram showing the state of the discharge portion of the immersion nozzle of Experimental Example H.
Figure 11i is a schematic diagram showing the state of the discharge portion of the immersion nozzle of Experimental Example I.
Figure 11j is a schematic diagram showing the state of the discharge portion of the immersion nozzle of Experimental Example J.
Figure 11k is a schematic diagram showing the state of the discharge portion of the immersion nozzle of Experimental Example K.
Figure 11l is a schematic diagram showing the state of the discharge portion of the immersion nozzle of experimental example L.
Figure 11m is a schematic diagram showing the state of the discharge portion of the immersion nozzle of experimental example M.
Figure 12 is a schematic diagram of a full-scale water model experiment.

Figure 1 shows a schematic diagram of a typical slab continuous casting device.

As illustrated in Fig. 1, molten steel S stored in a tundish T is supplied to a mold M through an immersion nozzle N.

Then, the supplied molten steel S is slowly cooled in the mold M and withdrawn, thereby continuously casting a slab.

The flow rate of molten steel S supplied from the tundish T to the immersion nozzle N is adjusted by a flow control mechanism such as a slide gate or stopper.

Meanwhile, as the flow rate is adjusted, fluctuations or biases occur in the downward flow within the immersion nozzle N.

When the immersion nozzle N is equipped with multi-porous discharge holes, the distribution of the flow rate to the multi-porous discharge holes changes due to fluctuations or bias in the downward flow, and bias also occurs in the flow of molten steel within the mold.

Figure 2 is a schematic diagram showing the state in which an imbalance occurs in the flow of molten steel within a mold.

As shown in Fig. 2, when the flow path of the molten steel is narrowed by the euro-diaphragm mechanism, a drift occurs inside the immersion nozzle.

And, when the molten steel with drift is discharged into the mold, drift also occurs in the flow of the molten steel within the mold.

If drift occurs within the mold, problems such as surface disturbance or stagnation may occur.

If a slab is cast in this fluid state, surface defects may occur in the manufactured slab because it affects the formation of the solidification shell.

In addition, suppressing the imbalance of the flow of molten steel within the mold can be said to be important from the perspective of stabilizing the casting operation.

Therefore, a technology to suppress the imbalance of molten steel flow within a mold is desired.

For this problem, the present inventors conducted an experimental review.

As a result, the inventors of the present invention found that by combining the following two elements, a self-stabilizing function of effective discharge distribution can be imparted to an immersion nozzle having multiple discharge holes.

The first element is to provide an internal barrier that can distribute the downstream flow from the tundish through the Euro-bridge mechanism to the left and right.

The second element is a mechanism for compensating for the left-right bias that occurs in the flow distribution of the first stage, by providing a distribution block below the internal barrier that can distribute the flow so that the distribution toward the side where the flow distribution was reduced in the first distribution increases.

The immersion nozzle of the present disclosure, which is made based on the above findings, is described in detail below.

[First embodiment]

FIG. 3 shows a cross-sectional view in the width direction passing through the axial center C of the immersion nozzle (100) according to the first embodiment.

Additionally, in the present disclosure, the left-right direction of FIG. 3 is called the width direction, the up-down direction is called the height direction, and the depth direction is called the thickness direction.

The immersion nozzle (100) according to the first embodiment is used to continuously cast a slab by discharging molten steel supplied from a tundish into a mold.

The immersion nozzle (100) is hollow and has a flow path for molten steel formed inside.

As shown in Fig. 3, the immersion nozzle (100) has a direct driving part (10) that receives molten steel supplied from a tundish, a discharge part (30) that supplies the molten steel to a mold, and a connecting part (20) that connects the direct driving part (10) and the discharge part (30).

The direct driving part (10) and the connecting part (20) are optional parts, but are usually provided in the immersion nozzle.

In addition, the immersion nozzle (100) has two regions R1 and R2 divided by a thickness direction plane passing through the axial center C (i.e., a plane parallel to the extension direction of the axial center C and the thickness direction).

Areas R1 and R2 are areas conveniently defined for the description of the immersion nozzle (100).

In the immersion nozzle (100), the regions R1 and R2 are usually shaped like plane symmetry.

“Axis center C” is the intersection of planes that divide the width direction length and thickness direction length of the immersion nozzle (100) into two equal parts.

Normally, the axis center C passes through the centers of the direct driving part (10), the connecting part (20), and the discharge part (30).

The center of each member is the intersection of planes that divide the width direction and thickness direction of each member into two equal parts.

In addition, the immersion nozzle (100) has two regions R3 and R4 divided by a widthwise plane passing through the axial center C (i.e., a plane parallel to the extension direction of the axial center C and the widthwise direction) (see FIG. 4).

In the immersion nozzle (100), the regions R3 and R4 may have a shape of surface symmetry.

In the immersion nozzle (100), it is common for regions R1 and R2 to have a shape of surface symmetry, and also for regions R3 and R4 to have a shape of surface symmetry.

The direct driving part (10) is a part of the tube that receives molten steel supplied from the tundish.

Figure 4 shows a plan view of an immersion nozzle (100).

As shown in Fig. 4, the direct driving part (10) has a flow path (11) of a certain shape formed inside it through which the downward flow of molten steel flows.

The size of the direct driving part (10) or the euro (11) can be appropriately set depending on the purpose.

As shown in Fig. 4, normally, the length in the thickness direction of each member (direct drive part (10), connection part (20), discharge part (30)) of the immersion nozzle (100) is approximately constant, and the length in the thickness direction of the internal flow path is also approximately constant.

“Approximately constant” means including manufacturing errors or circumstances (e.g., within ±1% of the specified length).

For example, there are cases where a slight taper is applied from top to bottom due to manufacturing circumstances.

Here, the length of the path (11) of the direct driving part (10) in the width direction is defined as W11, and the path area of the direct driving part (10) is defined as S11.

In this application, “channel area” means the area of a cross-section of a channel perpendicular to its central axis.

Since the central axis of the flow path of the direct driving part (10) extends in a straight line, the flow path area S11 of the direct driving part (10) is equal to the projected area of the flow path (11) of the direct driving part (10) on the horizontal plane.

The dimensions of the width direction length W11 of the euro (11) and the euro area S11 will be described later.

The shape of the cross section perpendicular to the axis center C of the direct driving part (10) is rectangular.

However, in the immersion nozzle of the present disclosure, the cross-sectional shape of the direct driving portion is not particularly limited, and may be circular, elliptical, or polygonal.

The connecting portion (20) is a portion that connects the direct driving portion (10) and the discharge portion (30), and has a path for allowing molten steel to flow from the direct driving portion (10) to the discharge portion (30).

The shape of the connecting portion (20) is not particularly limited.

In Fig. 3, the connecting portion (20) has a gentle slope from the direct driving portion (10) to the discharge portion (30).

The discharge portion (30) is a portion that supplies molten steel to the mold, and has an approximate fan shape that widens from the direct portion (10) side toward the bottom portion (31) side when viewed in the thickness direction.

In addition, the discharge portion (30) has a flat shape in which the length in the thickness direction is shorter than the length in the width direction.

The discharge portion (30) has a bottom portion (31) and a side wall (32) extending from the outer edge of the bottom portion (31).

As shown in Fig. 3, the bottom (31) is a portion that forms an area roughly equivalent to a fan-shaped arc.

The lower part of the side wall (32) is connected to the outer edge of the bottom part (31), and the upper part is connected to the outer edge of the connecting part (20).

The side wall (32) is a member that forms the outer side of the discharge portion (30), and contributes to the formation of a flow path for molten steel, for example, an outer discharge hole (33aa, 33ba) and a branch flow path (35) described later.

The approximate fan shape of the discharge portion (30) may be appropriately set depending on the configuration of the internal flow path or the angle of the discharge hole (33) with respect to the horizontal direction.

Figure 5 shows a bottom view of the immersion nozzle (100).

As shown in Fig. 5, the discharge portion (30) has four discharge holes (33).

As the number of discharge holes (33) increases, the discharge flow rate can be reduced by increasing the discharge hole area.

On the other hand, if the number of discharge holes (33) is too large, the outer dimensions of the immersion nozzle will be enlarged, which will cause problems in cost and operational handling.

In addition, when the number of discharge holes is odd, the discharge holes in the center of the width are directed directly downward from the perspective of maintaining left-right symmetry.

The discharge flow directed directly downward from the center of this width may interfere with the discharge flow from other discharge holes, resulting in instability in the flow within the mold.

Therefore, in the immersion nozzle (100) of the present disclosure, since the number of discharge holes is four, it is possible to suppress the uneven flow of molten steel within the mold.

Additionally, the discharge hole (33) is arranged at the bottom (31) of the discharge portion (30).

More specifically, two discharge holes (33) are arranged side by side in the width direction in each of regions R1 and R2.

As shown in Fig. 5, the discharge holes (33) may be arranged in a straight line in the width direction.

In Fig. 5, the shape of the discharge hole (33) is rectangular when viewed from the bottom.

However, in the immersion nozzle of the present disclosure, the shape of the discharge hole is not limited to this, and may be circular, oval, or polygonal.

Here, among the two discharge holes (33) arranged in each of regions R1 and R2, the discharge hole (33) arranged on the outer side in the width direction is defined as an outer discharge hole (33aa, 33ba), and the discharge hole (33) arranged on the inner side in the width direction is defined as an inner discharge hole (33ab, 33bb).

Returning to Fig. 3, the configuration of the discharge portion (30) is further described.

The discharge portion (30) has an internal barrier (34), a branch flow path (35), and a distribution block (36).

The inner barrier (34) is placed in the center of the width direction and distributes the molten steel (downward flow) supplied from the tundish to each area R1 and R2.

The branch flow path (35) is a path that flows between each of the side walls (32) and the inner barrier (34) of regions R1 and R2, and distributes the molten steel (branch flow) by the inner barrier (34).

The distribution block (36) is placed on the lower (31) side than the inner barrier (34), and further distributes the branch flow passing through the branch flow path (35) in each of the regions R1 and R2, and supplies it to at least three discharge holes (33).

The inner barrier (34) is located closer to the direct driving part (10) than the distribution block (36), and is also positioned lower than the lower end of the direct driving part (10).

The inner barrier (34) has the role of distributing the downflow (molten steel) supplied from the direct driving section (10) to each of the regions R1 and R2 (one side and the other side in the width direction).

That is, the inner barrier (34) is a member that carries out the first stage of distribution of the molten steel.

The branch flow path (35) is formed between the side surface (34c) of the inner barrier (34) and the side wall (32), thereby allowing the branch flow distributed by the inner barrier (34) to flow.

After passing through the branch flow path (35), the branch flow is discharged into the mold from the discharge hole (33).

Some of the branch flows are discharged as they are from the outer discharge holes (33aa, 33ba), but some of the branch flows collide with the distribution block (36) and are distributed to at least three discharge holes (33).

The distribution block (36) is placed on the lower (31) side rather than the inner barrier (34).

The distribution block (36) is a member that further distributes the branch flow passing through the branch flow path (35) in each of areas R1 and R2 and supplies it to at least three discharge holes (33).

That is, the distribution block (36) is a member that performs the second stage of distribution of the molten steel.

“At least three discharge holes (33)” means at least inner discharge holes (33ab, 33bb) and outer discharge holes in the area where the distribution block (36) is arranged.

For example, if we focus on a distribution block (36) placed in area R1, the outer discharge hole of area R1 where the distribution block (36) is placed is an outer discharge hole (33aa).

In this way, the discharge unit (30) performs a two-stage distribution on the molten steel supplied from the tundish, and averages the flow rate of the molten steel discharged from each discharge hole (33), thereby suppressing unevenness.

That is, even if flow rate imbalance occurs due to flow rate distribution in the first stage using the internal barrier (34), the discharge unit (30) can correct the flow rate distribution imbalance by the flow rate distribution in the second stage using the distribution block (36).

However, there are cases where the flow distribution function cannot be sufficiently achieved simply by providing an internal barrier (34) or a distribution block (36).

Therefore, in the immersion nozzle (100), an internal barrier (34) and a distribution block (36) are provided so that the following features 1 and 2 can be exhibited.

(Feature 1)

When one of the branch flow paths (35) is blocked, the flow rate of molten steel discharged from the inner discharge hole located in the area where the branch flow path (35) is blocked is greater than the flow rate of molten steel discharged from the inner discharge hole located in the area where the branch flow path (35) is not blocked.

That is, for example, when the branch flow path (35) of area R1 (the elliptical portion surrounded by a broken line in Fig. 3) is blocked, the flow rate of molten steel discharged from the inner discharge hole (33ab) arranged in area R1 is greater than the flow rate of molten steel discharged from the inner discharge hole (33bb) arranged in area R2.

This means that the branch flow that collides with the distribution block (36) of area R2 is mainly supplied to the inner discharge hole (33ab) of area R1 rather than the inner discharge hole (33bb) of area R2.

Since the immersion nozzle (100) has this feature 1, even if flow rate imbalance occurs due to the flow rate distribution of the first stage using the internal barrier (34), the immersion nozzle (100) can correct the flow rate distribution imbalance by the flow rate distribution of the second stage using the distribution block (36).

That is, it can be said that the immersion nozzle (100) is provided with a self-stabilizing function for the distribution of discharged fluid.

By using an immersion nozzle having such features, it is possible to suppress the uneven flow of molten steel within the mold.

It is possible to determine whether the immersion nozzle satisfies the above characteristics by conducting a full-scale water model experiment. In the water model experiment, the flow rates a and b are measured when one of the branch flow paths is blocked.

Flow rate a: The flow rate of water discharged from the inner discharge hole located in the area where the branch flow path is blocked.

Flow rate b: The flow rate of water discharged from the inner discharge hole located in an area where the branch flow path is not blocked.

If the flow rate a is greater than the flow rate b, it can be determined that feature 1 is satisfied.

The reason why this can be judged by the above water model experiment is that since the dynamic viscosity of molten steel and water is almost the same, the way the molten steel flows and the way the water flows inside the immersion nozzle can be considered to be the same.

The experimental conditions adopt the same flow rate/flow conditions as actual operating conditions.

For example, the flow rate of the downstream flow passing through the direct current section (10) is set to the same conditions as the actual operating conditions.

Additionally, the time for flowing water into the immersion nozzle (100) is set to at least 1 minute.

By this, it is possible to check with high precision whether feature 1 is present.

There is no particular limitation to the method for occluding the branch flow path (35) in the water model experiment, but for example, a rubber stopper or the like that is tailored to the cross-sectional shape of the branch flow path (35) may be used to occlude the area indicated by the dashed ellipse in Fig. 3.

The above feature 1 can be rephrased as follows.

When one of the branch flow paths (35) is blocked, the flow rate of molten steel discharged from the inner discharge hole located in the area where the branch flow path (35) is blocked is defined as Qa, and the flow rate of molten steel discharged from the inner discharge hole located in the area where the branch flow path (35) is not blocked is defined as Qb, then Qa/Qb satisfies the following equation (1).

Qa/Qb>1.0 … (1)

From the viewpoint of more reliably demonstrating the self-stabilizing function, the value of Qa/Qb is preferably 1.1 times or more, and more preferably 1.2 times or more.

On the other hand, when the value of Qa/Qb exceeds 3 times, there are cases where the flow redistribution to obtain the self-stabilizing function becomes excessive.

In this case, there are cases where the flow drifts towards the euro blockage side.

Therefore, it is desirable that the value of Qa/Qb be less than 3 times.

The value of Qa/Qb can be less than or equal to 2.1 times, less than or equal to 1.9 times, or less than or equal to 1.5 times.

In addition, there are cases where the ratio of the flow rate of molten steel discharged from an inner discharge hole arranged in an area where the branch flow path (35) is blocked to the flow rate of molten steel discharged from an inner discharge hole arranged in an area where the branch flow path (35) is not blocked is referred to as a distribution ratio.

(Feature 2)

The relationship between the discharge flow rate Q _out of molten steel discharged from the outer discharge holes (33aa, 33ba) and the discharge flow rate Q _IN of molten steel discharged from the inner discharge holes (33ab, 33bb) satisfies equation (2).

0.1≤Q _IN /Q _out ≤1.0 … (2)

Here, the discharge flow rate Q _out is the sum of the flow rates discharged from the outer discharge holes (33aa, 33ba), and the discharge flow rate Q _IN is the sum of the flow rates discharged from the inner discharge holes (33ab, 33bb).

In equation (2), the upper limit of Q _IN /Q _out is set to 1.0.

That is, the discharge flow rate Q _IN from the inner discharge hole (33ab, 33bb) does not exceed the discharge flow rate Q _out from the outer discharge hole (33aa, 33ba).

From the viewpoint of stability of the flow within the mold, it is desirable that the discharge flow from the outer discharge holes (33aa, 33ba) be the main one, since formation of a clear collision pattern with the short-side solidification shell of the discharge flow is necessary.

Of course, an excessive collision velocity is dangerous and undesirable from the viewpoint of preventing re-melting of the solidification shell, but as a flow pattern, forming a clear pattern toward the short-sided solidification shell is desirable in that it forms a more stable flow.

From the perspective of forming a more stable flow, it is desirable that the upper limit of Q _IN /Q _out be 0.8 or less, and more desirable that it be 0.6 or less.

In equation (2), the lower limit of Q _IN /Q _out is set to 0.1.

That is, the discharge flow rate Q _IN from the inner discharge hole (33ab, 33bb) is secured to be 0.1 times or more greater than the discharge flow rate Q _out from the outer discharge hole (33aa, 33ba).

This is in line with the original purpose of the present disclosure, which is to distribute the discharged fluid to the inner discharge holes (33ab, 33bb) to stabilize the flow within the mold.

The lower limit of Q _IN /Q _out can be 0.2 or higher.

The discharge flow rates Q _out and Q _IN can be calculated by conducting a full-scale water model experiment and measuring the amount of water discharged from each discharge hole.

As described above, since the viscosity of molten steel and water is almost the same, the way the molten steel flows and the way the water flows inside the immersion nozzle can be considered to be the same.

The experimental conditions adopt the same flow rate/flow conditions as actual operating conditions.

For example, the flow rate of the downstream flow passing through the direct current section (10) is set to the same condition.

Additionally, the time for flowing water into the immersion nozzle (100) is set to at least 1 minute.

By this, it is possible to check with high precision whether feature 2 is present.

In the case of the immersion nozzle (100), if it has not only the above features 1 and 2 but also the following feature 3, the immersion nozzle (100) is preferable because it can more sufficiently exhibit the flow rate distribution function.

(Feature 3)

In each of regions R1 and R2, the outer discharge angle α1, which is defined from the angle of the wall surface forming the outer discharge holes (33aa, 33ba), is between 40° downward and 75° downward, and further, the relationship with the inner discharge angle α2, which is defined from the angle of the wall surface forming the inner discharge holes (33ab, 33bb), satisfies equation (3).

The downward angle is the angle with respect to the width direction.

-5°≤|α2|-|α1|≤15° … (3)

The outer discharge angle α1 and the inner discharge angle α2 are determined from the cross-sectional shape of the immersion nozzle (100) divided into a width-direction plane passing through the axis center C.

The outer discharge angle α1 is adopted as the angle of the wall surfaces opposing the outer discharge holes when the angles of those wall surfaces are the same, and is adopted as the average value of these angles when the angles of the opposing wall surfaces of the outer discharge holes are different.

Similarly, the inner discharge angle α2 is adopted as the angle of the opposing wall surfaces of the inner discharge hole when the angles of the opposing wall surfaces of the inner discharge hole are the same, and is adopted as the average value of these angles when the angles of the opposing wall surfaces of the inner discharge hole are different.

In addition, the outer discharge holes (33aa, 33ba) and inner discharge holes (33ab, 33bb) sometimes have a tapered or curved surface at the entrance or exit of the holes to facilitate the entry and exit of molten steel.

In this case, the discharge angle is calculated, excluding taper or curve.

The outer discharge angle α1 and the inner discharge angle α2 are calculated for each region R1 and each region R2, and any region must satisfy equation (3).

When high-speed casting with a casting speed of 3 m/min or more is assumed, from the viewpoint of suppressing undulation of the molten metal surface inside the mold, it is preferable that the outer discharge angle α1 be 40° or more downward, and it is more preferable if it is 45° or more downward.

Meanwhile, since an excessive discharge angle causes instability in the flow within the mold, it is desirable that the outer discharge angle α1 be limited to 75° downward, and a more desirable upper limit is 65° downward.

In addition, the relationship between the outer discharge angle α1 and the inner discharge angle α2 satisfies equation (3).

(3) The meaning of the formula is as follows.

Normally, from the viewpoint of dissipating kinetic energy by dissipating the discharge flow, the inner discharge angle α2 is set to be larger than the outer discharge angle α1.

The inventors of the present invention have found, through experimental and numerical analysis, that when the values of the two discharge angles are close, the discharge streams tend to attract each other and merge.

In addition, the inventors of the present invention found that, in the self-stabilizing function by the distribution block (36), the tendency for the outer discharge flow and the inner discharge flow to merge works advantageously.

Based on this, it was found that the difference between the inner discharge angle α2 and the outer discharge angle α1 is preferably 15° or less.

It is more desirable if this angle difference is less than 10°.

On the other hand, if the difference between the two is set to minus, that is, the inner discharge angle α2 is set smaller than the outer discharge angle α1, it is disadvantageous for the dissipation of kinetic energy due to dispersion of the discharge flow, so the minimum value of the difference between the two is set to -5°.

It is more preferable that the above minimum value be 0, that is, that the inner discharge angle α2 and the outer discharge angle α1 are the same value.

The shape of each member of the immersion nozzle (100) is appropriately set so as to have the above-mentioned flow distribution characteristics.

The shape of an immersion nozzle having flow distribution characteristics is achieved by strictly adjusting the shape (shape, size, arrangement, etc.) of each member, but the shape is so diverse that it is difficult to explain all the shapes.

Below, each member of the immersion nozzle (100) is described, but these are examples.

The shape of the immersion nozzle of the present disclosure is not limited as long as it has flow distribution characteristics.

The discharge portion (30) has a roughly fan shape, and four discharge holes (33) are arranged in the lower portion (31).

These discharge holes (33) are appropriately set in terms of placement location, hole size, angle, etc. to realize flow distribution characteristics.

Normally, the angle of the inner discharge hole (33ab, 33bb) is set larger than the angle of the outer discharge hole (33aa, 33ba).

The angle of the discharge hole is the angle formed by a straight line dividing the width of the discharge hole (e.g., the width of the outer opening) in half and a straight line extending in the width direction in the cross-section passing through the center C of the axis.

For example, the angle of the inner discharge hole (33ab, 33bb) may be 60° or more, 70° or more, 75° or more, or 90° or less.

The angle of the outer discharge hole (33aa, 33ba) may be 40° or more, 50° or more, 60° or more, 90° or less, or 75° or less.

The inner barrier (34) has the role of distributing the downflow (molten steel) supplied from the direct driving section (10) to area R1 and area R2 (one side and the other side in the width direction).

In addition, the inner barrier (34) is located closer to the direct driving part (10) than the distribution block (36), and is also positioned below the lower part of the direct driving part (10).

From the viewpoint of appropriately distributing the downflow to regions R1 and R2 (one side and the other side in the width direction), the inner barrier (34) may be completely closed between the inner barrier (34) and the side wall (32) in the thickness direction.

In other words, the internal barrier (34) may be formed across the thickness direction of the discharge portion (30).

In Fig. 6, a projection drawing of the immersion nozzle (100) is shown on a horizontal plane (a plane formed from the width direction and the thickness direction), and a drawing focusing on the flow path (11) and the internal barrier (34) is shown.

When the inner barrier (34) is projected onto a horizontal plane, the projection area S34 is preferably greater than the flow path area S11 of the direct driving section (10).

By this, the bias in the distribution of the downstream flow into regions R1 and R2 can be effectively suppressed.

From the viewpoint of more effective suppression, it is more preferable that the projection area S34 of the inner barrier (34) be 1.2 times or more the flow path area S11 of the direct driving section (10), and more preferably 1.5 times or more.

Meanwhile, since the flow rate decreases when the projection area S34 of the inner barrier (34) is excessively large, it is preferable that the projection area S34 of the inner barrier (34) be 3 times or less than the flow path area S11 of the direct driving section (10), and more preferably 2 times or less.

Figure 7 shows an enlarged view of the inner barrier (34).

The inner barrier (34) has an upper surface (34a) on the direct driving part (10) side, a lower surface (34b) on the lower part (31) side, and a side surface (34c) connecting the upper surface (34a) and the lower surface (34b).

The upper surface (34a) is the surface of the inner barrier (34) that receives the molten steel (downward flow) supplied from the tundish (direct-moving part (10)).

The downflow can be distributed to regions R1 and R2 by the upper surface (34a).

As shown in FIG. 3 and FIG. 7, it is preferable that the upper surface (34a) has a concave portion (34aa).

The concave portion (34aa) has a bottom portion (34aa1) and a side portion (34aa2) extending from both ends of the bottom portion (34aa1), thereby being open on the side of the direct driving portion (10).

The immersion nozzle (100) has a concave portion (34aa), thereby suppressing the flow rate bias of the branch flow.

In other words, the self-stabilizing function can be further enhanced.

However, the upper surface of the inner barrier of the present disclosure does not need to have a concave portion.

For example, the upper surface of the inner barrier may be flat.

The present inventors estimate the following mechanism for the effect by the concave portion (34aa).

That is, when a downward flow collides with an internal barrier (34) and the downward flow is distributed as a branch flow to regions R1 and R2, and there is an imbalance in the flow rate of the branch flow, it is estimated that a part of the branch flow with a large flow rate is splashed along the surface from the side portion (34aa2) of the concave portion (34aa) to the bottom portion (34aa1), and the splashed molten steel is applied to the branch flow with a small flow rate, thereby suppressing the imbalance in the flow rate of the branch flow.

The concave portion (34aa) may be arranged on the entire upper surface (34a) or may be arranged on a part of the upper surface (34a).

When a concave portion (34aa) is arranged on a part of the upper surface (34a), the concave portion (34aa) is arranged in the center in the width direction, as shown in Fig. 7.

The projected area S34aa (projected area of the opening) of the concave portion (34aa) projected on the horizontal plane is not particularly limited, but may be approximately the same as the flow path area S11 of the direct driving portion (10).

By this, the effect of suppressing the flow rate bias of the branch flow can be further improved.

If the projection area S34aa of the concave portion (34aa) is too small, the effect of forming the concave portion (34aa) is not sufficiently obtained, so the projection area S34aa of the concave portion (34aa) is preferably 0.8 times or more the flow path area S11 of the direct driving portion (10), and more preferably 0.9 times or more.

Meanwhile, if the projection area S34aa of the concave portion (34aa) is too large, the internal barrier (34) itself also becomes larger, so the projection area S34aa of the concave portion (34aa) is preferably 1.5 times or less the flow path area S11 of the direct driving portion (10), and more preferably 1.2 times or less.

The depth of the concave portion (34aa) (length in the height direction from the bottom portion (34aa1) to the end surface (34ae)) H34aa is not particularly limited, but is preferably set as follows.

It is preferable that the depth H34aa of the concave portion (34aa) be 10 mm or more.

By setting it this way, the effect of suppressing the flow rate bias of the branch flow is more reliably obtained.

The depth H34aa of the concave portion (34aa) is preferably 30 mm or less, and more preferably 20 mm or less.

By setting it this way, it is possible to avoid the nozzle outer dimensions becoming unnecessarily large.

The projection area S34aa1 of the bottom surface (34aa1) is not particularly limited, but in order to avoid an unnecessarily large nozzle external dimension, it is preferably 1.0 times or less of the projection area S34aa (projection area of the opening) of the concave portion (34aa), more preferably 0.9 times or less, and even more preferably 0.8 times or less.

The projection area S34aa1 of the lower surface (34aa1) may be 0.5 times or more, or 0.6 times or more, of the projection area S34aa of the concave portion (34aa).

The side portion (34aa2) may be formed perpendicular to the bottom surface (34ab) or may have an incline.

When the side portion (34aa2) has a slope, the slope may be linear or curved.

When a concave portion (34aa) is arranged on a part of the upper surface (34a), an end surface (34ae) is arranged between the end of the upper surface (34a) and the concave portion (34aa).

The end face (34ae) may be horizontal or may have an incline.

The slope of the end face (34ae) may be lower or higher toward the inside. Alternatively, the end face (34ae) may be a curved surface.

The lower surface (34b) may have a sloped portion (34ba) whose height decreases toward the inside.

In order to form the distribution flow path (36b) described later, at least the inclined portion (34ba) may be positioned opposite the upper surface (36a) of the distribution block (36).

In Fig. 3 and Fig. 7, inclined portions (34ba) are arranged at both ends in the width direction of the lower surface (34b).

The lower surface (34b) may have a horizontal plane (34bb) that defines the lower height of the inclined portion (34ba).

Alternatively, the entire surface (34b) may be a horizontal surface (34bb).

For example, when the distance from the upper surface (36a) of the distribution block (36) to the lower surface (34b) is large, it does not matter if there is no inclined portion (34ba) and the lower surface is entirely horizontal (34bb).

When the lower surface (34b) is a horizontal surface (34bb), a distribution flow path (36b) is formed from the horizontal surface (34bb) and the upper surface (36a) of the distribution block (36).

The side (34c) has the role of forming a branch flow path (35) together with the side wall (32).

The shape of the side (34c) is not particularly limited, and may be a plane, a vertical surface, an inclined surface, a curved surface, or a shape combining these.

Additionally, the side (34c) may be inclined so that its height decreases toward the outside in the width direction.

By this, the branch flow can be made smooth.

Next, the branch flow path (35) will be described.

As described above, the branch flow path (35) is formed between the side surface (34c) of the inner barrier (34) and the side wall (32).

The flow path area S35 of the branch flow path (35) is not particularly limited, but if it is too small, it may hinder high-speed casting, so it is preferably 0.4 times or more the flow path area S11 of the direct driving section (10), and more preferably 0.5 times or more.

Meanwhile, if the flow path area S35 of the branch flow path (35) is too large, there are cases where the self-stabilizing function is not sufficiently obtained. Therefore, the flow path area S35 of the branch flow path (35) is preferably 1.5 times or less than the flow path area S11 of the direct driving part (10), and more preferably 1 time or less.

The flow path area S35 of a branch flow path (35) refers to the minimum flow path area of one branch flow path (35).

For example, in a case where the flow path area of a branch flow path (35) as described below gradually decreases downward, the flow path area of the branch flow path (35) at the position where the flow path area becomes the smallest is regarded as the minimum flow path area.

In the case where the flow path area S35 of the branch flow path (35) is different on the left and right, the minimum flow path area of the branch flow path (35) on the side with the smaller flow path area S35 is regarded as the flow path area S35 of the branch flow path (35).

The area S35 of the branch flow path (35) may be of an irregular shape.

For example, the area S35 of the branch flow path (35) may be reduced.

Even in this case, the flow path area S35 (minimum flow path area) of the branch flow path (35) may be made to satisfy the above range.

A branch flow path (35) like this can be formed by adjusting the inclination angle of the side (34c) and/or the side wall (32).

If the flow area S35 of the branch flow path (35) is in a form of decreasing, the branch flow can be appropriately guided to the distribution block (36) to further enhance the self-stabilizing function compared to the case where the flow area S35 is in a form of increasing.

Continuing, the distribution block (36) is described.

The distribution block (36), as described above, is a member that further distributes the branch flow that has passed through the branch flow path (35) and supplies it to each discharge hole (33), and is a member that performs the second stage of distribution of the downward flow.

Here, the distribution ratio of the branch flow can be controlled by the shape of the distribution block (36).

By controlling the distribution ratio, the imbalance in flow distribution can be suppressed.

Below, the shape of the distribution block (36) is described.

Figure 8 shows an enlarged view of the bottom (31) side of the discharge portion (30).

As shown in Fig. 8, the distribution block (36) is placed in each of the areas R1 and R2, is a partition wall separating the outer discharge hole and the inner discharge hole, and is a part of the bottom (31).

Additionally, the bottom (31) has a central block (37) separating two inner discharge holes (33ab, 33bb).

Since the distribution block (36) has the role of distributing the branch flow, it has a characteristic on the upper surface (36a) that collides with the branch flow.

The side and bottom of the distribution block (36) may be appropriately set according to the shape of the discharge hole (33).

In the example shown in Fig. 8, the distribution block (36) has a shape close to a trapezoid.

The upper surface (36a) of the distribution block (36) is composed of a first portion (36aa) facing the inner barrier (34) and a second portion (36ab) other than that.

However, the shape of the distribution block (36) is not limited to this, and may have only a second portion (36ab), may be configured by combining many planes with different angles, or may be formed as a complex curved surface.

When the point C where the A-B line segment connecting the outer end A and the inner end B of the upper surface (36a) of the distribution block (36) intersects with the extension line L of the side surface (34c) of the inner barrier (34) is defined, the first portion (36aa) and the second portion (36ab) can be defined as follows.

Part 1 (36aa) = Range between inner end B and intersection C

Part 2 (36ab) = Range between outer end A and intersection C

The first part (36aa) mainly contributes to the formation of a branch flow path (distribution flow path (36b)) distributed to the inner discharge hole side.

The distribution flow path (36b) is formed between the lower surface (34b) (sloping portion (34ba)) of the inner barrier (34) and the upper surface (36a) of the distribution block (36), and supplies the branch flow to two inner discharge holes (33ab, 33bb).

At this time, for example, when paying attention to the shape of the upper surface of the distribution flow path (36b) and the central block (37) on the area R1 side, the shape of the upper surface of the distribution flow path (36b) and the central block (37) is set so as to increase the ratio of the branch flow distributed to the inner discharge hole (33bb) more than to the inner discharge hole (33ab).

In this way, the imbalance in flow distribution can be corrected.

A distribution flow path (36b) that exerts such an effect can be realized by, for example, setting the shapes of the inner barrier (34), the distribution block (36), and the central block (37) so that the flow of molten steel (streamline F) passing through the distribution flow path (36b) simply passes over the inner discharge hole (33ab) of the same area and heads toward the inner discharge hole (33bb) of another area.

The streamline F can be identified as the direction of the mainstream by flowing a tracer (e.g. microbubbles or ink) that visualizes the flow in a water model experiment.

In Fig. 8, a streamline close to the center line of the slope (34ba) of the inner barrier and the upper surface (36a) of the distribution block is conveniently illustrated.

The streamlines here are not geometrically obtained streamlines, but rather experimentally obtained streamlines.

The flow path area S36b of the distribution flow path (36b) is not particularly limited, but is preferably at least 0.3 times the flow path area S11 of the direct driving section (10), and more preferably at least 0.4 times the flow path area S11.

The flow path area S36b of the distribution flow path (36b) is preferably 1.5 times or less than the flow path area S11 of the direct driving section (10), and more preferably 1 time or less.

The area of the distribution channel (36b) S36b refers to the minimum area of the distribution channel (36b).

For example, in a case where the flow path area S36b of the distribution flow path (36b) is gradually reduced toward the downward (downstream) direction, the flow path area of the distribution flow path (36b) at the position where the flow path area becomes the smallest is regarded as the minimum flow path area.

In the case where the flow path area S36b of the distribution flow path (36b) is different on the left and right, the minimum flow path area of the distribution flow path (36b) on the side with the smaller flow path area S36b is regarded as the flow path area S36b of the distribution flow path (36b).

The second portion (36ab) contributes to the distribution ratio when further distributing the branch flow distributed by the inner barrier (34) to the outer discharge hole side and the inner discharge hole side.

The length L36a (between points A-B) of the upper surface (36a) is not particularly limited, but is preferably at least 0.3 times the length W11 in the width direction of the flow path (11), and more preferably at least 0.8 times the length.

The length L36a of the upper surface (36a) is preferably 1.5 times or less than the length W11 in the width direction of the euro (11), and more preferably 1.0 times or less.

The ratio L36aa:L36ab of the length L36aa (point D-point B) of the first part (36aa) and the length L36ab (point A-point D) of the second part (36ab) is not particularly limited, but is, for example, between 1:4 and 3:2.

The angle β (the angle formed by the straight line passing through points A and B and the straight line along the width direction) of the upper surface (36a) is not particularly limited and may be appropriately set according to the streamline F.

For example, in a typical design, the range is from 20° downward to 60° downward.

In addition, although the upper surface (36a) of the distribution block (36) in Fig. 8 shows a flat shape, the upper surface (36a) of the distribution block may be a combination of multiple planes having different angles or may be a curved surface.

Alternatively, the upper surface (36a) of the distribution block (36) may have a concave portion or a convex portion.

[Second embodiment]

The second embodiment is an immersion nozzle (200) in which the distribution block (36) of the first embodiment is configured independently from the bottom (31) of the discharge portion (30).

Below, the immersion nozzle (200) will be described, but the description of the common configuration with the immersion nozzle (100) will be omitted.

The immersion nozzle (200) has a discharge portion (130) independent of the distribution block (136) from the bottom (131).

Fig. 9 shows a cross-sectional view in the width direction passing through the axial center C of the discharge portion (130) of the immersion nozzle (200).

In addition, Fig. 10 shows an enlarged view of the bottom (131) side of the discharge portion (130).

As shown in FIG. 9 and FIG. 10, the immersion nozzle (200) is provided with a distribution block (136) independent from the bottom (131) in each area R1 and R2.

Accordingly, a partition (131a) is arranged in the lower part (131) to separate the outer discharge hole and the inner discharge hole.

Additionally, by making the distribution block (136) an independent configuration, the shape of the internal barrier (134) is also changed.

The distribution block (136) has a top surface (136a) similar to that of the distribution block (36).

For example, the distribution flow path (136b) is formed so that the streamline F of the distribution flow path (136b) is included in the upper surface of the bottom (131) of another area.

In this way, the imbalance in flow distribution can be corrected.

Other configurations of the distribution block (136) are not particularly limited.

For example, the distance between the distribution block (136) and the bottom (131) is not particularly limited, and may be appropriately set so that the immersion nozzle (200) has flow rate distribution characteristics.

From the above, the immersion nozzle of the present disclosure has been described based on the first embodiment and the second embodiment.

The immersion nozzle of the present disclosure corrects the flow rate distribution bias by the second-stage flow rate distribution using the distribution block even when the flow rate distribution bias occurs due to the first-stage flow rate distribution using the internal barrier.

Therefore, the immersion nozzle of the present disclosure can suppress the bias of the flow within the mold.

Example

Below, the immersion nozzle of the present disclosure is further described by experimental examples.

The appearance of the discharge portion (30A to 30M) of the immersion nozzle used in Experimental Examples A to M is illustrated in Figs. 11a to 11m.

Figures 11a to 11m illustrate cross-sectional views of the immersion nozzle in the width direction.

The structure and conditions of the immersion nozzles (30A to 30M) used in Experimental Examples A to M are shown in Table 1.

In all of Experimental Examples A to M, a linear member having a cross-sectional dimension of 56 mm in width and 31 mm in thickness was used.

In experiments A to C, G, H, J, K, and M, an internal barrier with a maximum width of 79 mm was used.

In experiments D, E, and I, an internal barrier with a maximum width of 50 mm was used.

In Experimental Example F, an internal barrier with a maximum width of 112 mm was adopted.

In Experimental Example L, no internal barrier was employed.

Among the experimental examples A to K and M employing an internal barrier, in the experimental examples A, B, E to H, J, K and M, a concave portion was provided in the internal barrier.

Among the experimental examples A to K and M that employed an internal barrier, in the experimental examples C, D and I, a concave portion was not provided in the internal barrier.

In Experimental Examples A to C, E to H, J, and K, an “integral” form in which the distribution block also serves as the lower outer wall was adopted.

In Experimental Example D, a “separated” form was adopted in which the distribution block was independent from the bottom surface.

In comparative examples I and M,

Qa/Qb>1.0 … (1)

0.1≤Q _IN /Q _out ≤1.0 … (2)

There are no internal barriers or distribution blocks provided to meet the requirements.

Specifically, in Experimental Example I, the inner barrier was placed higher than in the other Experimental Examples, and in Experimental Example M, the shape of the baffle separating the outer discharge hole and the inner discharge hole was adjusted to be thin, thereby designing the second stage flow rate distribution so that it could not be realized.

In experimental example L, which is a comparative example, since no internal barrier is provided, no branch flow exists and therefore no distribution flow exists.

In experimental examples A to I, L, and M, a configuration was used in which four discharge holes were provided.

In Experimental Example J, a configuration was used in which three discharge holes were provided.

In Experimental Example K, a configuration was used in which five discharge holes were provided.

In experimental examples A, E to H, the angle difference was set to 5° by setting the outer discharge hole discharge angle α1 = 50° and the inner discharge hole discharge angle α2 = 55°.

In experimental examples B to E, I, L, and M, the angle difference was set to 25° by setting the outer discharge hole discharge angle α1 = 50° and the inner discharge hole discharge angle α2 = 75°.

For each of Experimental Examples A to M,

·Projected area of the inner barrier/Area of the flow path of the direct part

· Euro area of branch flow/Euro area of direct flow

· Euro area of distribution type Euro/Euro area of direct driving part

The values are as shown in Table 1.

In Experimental Examples A to I and M, the values of Qa/Qb were obtained by conducting a water model experiment with the area on the left side of the inner barrier of the immersion nozzle completely occluded.

Specifically, water was supplied to the immersion nozzle at a predetermined downward flow rate in the cross-sectional area of the direct driving section, and the flow rate of water discharged from the left and right inner discharge holes was measured.

The “downward flow velocity” in each experimental example is as shown in Table 1.

Then, the flow rate of water discharged from the inner discharge hole on the left was designated as Qa, and the flow rate of water discharged from the inner discharge hole on the right was designated as Qb, and the value of Qa/Qb was calculated.

In addition, for experimental examples J and K having an odd number of discharge holes and experimental example L having no internal barrier, the values of Qa and Qb specified in the present invention cannot be measured, and therefore, a hyphen (-) is indicated in Table 1.

In Experimental Examples A to I, L, and M, the values of Q _IN /Q _OUT were obtained by conducting a water model experiment.

Specifically, water was supplied to the immersion nozzle at a predetermined downward flow rate in the cross-sectional area of the direct driving section, and the flow rate of water discharged from the left and right inner discharge holes and the left and right outer discharge holes was measured.

The “downward flow velocity” in each experimental example is as shown in Table 1.

Then, the discharge flow rate of water discharged from the outer discharge hole (sum of left and right) was set as Q _out , and the discharge flow rate of water discharged from the inner discharge hole (sum of left and right) was set as Q _IN , and the value of Q _IN /Q _out was obtained.

In addition, for experimental examples J and K where the number of discharge holes is odd, the values of Q _IN and Q _out specified in the present invention cannot be measured, so a hyphen (-) is entered in Table 1.

For Experimental Examples A to M, the flow stability index and drift index were evaluated to confirm the effectiveness of the present invention.

Using the immersion nozzles of Experimental Examples A to M, full-scale water model experiments were conducted to evaluate the stability of the flow within the mold.

Figure 12 shows a schematic diagram of the full-scale water model experiment.

Additionally, the experimental conditions are shown in Table 2.

First, a full-scale water model experiment was conducted in which water was injected without any cross-talk.

When the water injection condition is no-collision, since a left-right symmetrical downward flow enters the nozzle, left-right drift hardly occurs on a time average basis.

Meanwhile, even in the case of no axle, a phenomenon of left-right self-excited oscillatory drift occurs with a cycle of several tens of seconds to several minutes.

Therefore, the degree of variation was evaluated using the standard deviation of the horizontal velocity fluctuations at the velocity measurement points divided by the average velocity as a parameter.

This parameter was used as the flow stability index, and was evaluated using the average value of the values calculated at each of the left and right flow velocity measurement points.

The flow rate measurement time was 15 minutes per condition.

Next, a full-scale water model experiment was conducted under the condition that the water injection conditions were asymmetrical, the left half of the nozzle inlet was closed, and water was introduced into the nozzle only through the right half.

Since the asymmetric downflow causes left-right drift, the absolute value of the left-right difference in the horizontal velocity at the velocity measurement point of the drift was divided by the left-right average value of the horizontal velocity and used as a parameter for evaluation.

This parameter was used as the drift index.

The flow rate measurement time was 15 minutes per condition.

The results are shown in Table 3.

Experimental examples A to H, which satisfied the appropriate conditions, had a smaller flow stability index than experimental examples I to M, indicating that the flow within the mold was stable.

This is an immersion nozzle,

Qa/Qb>1.0 … (1)

0.1≤Q _IN /Q _out ≤1.0 … (2)

By having internal barriers and distribution blocks arranged in a manner that satisfies the requirements, the effect of suppressing temporary drift caused by fluctuations in the flow within the immersion nozzle is exerted, and as a result, it is shown that fluctuations in the flow within the mold can also be suppressed.

That is, it can be seen that the immersion nozzle has an internal barrier and distribution block, thereby providing a self-stabilizing function for the discharge flow distribution, which is effective against temporary drift phenomenon due to fluctuations.

In addition, experimental examples A to H, which meet suitable conditions, have a smaller drift index than experimental examples I to M, indicating that the flow within the mold is stable.

This shows that the immersion nozzle has an internal barrier and distribution block, which has the effect of suppressing the time-averaged drift caused by the bias of the downward flow above the immersion nozzle, and as a result, the bias of the flow within the mold can also be suppressed.

That is, the immersion nozzle

Qa/Qb>1.0 … (1)

0.1≤Q _IN /Q _out ≤1.0 … (2)

By having internal barriers and distribution blocks arranged in a manner that satisfies the requirements, a self-stabilizing function for discharge distribution is provided, and it can be seen that it is effective against a time-averaged drift phenomenon caused by external disturbance.

As shown in the experimental examples above, the immersion nozzle of the present disclosure can maintain stable flow within the mold by exhibiting a self-stabilizing function for both the time-averaged drift phenomenon caused by external disturbance and the self-excited oscillatory drift phenomenon caused by fluctuation.

According to the immersion nozzle of the present disclosure, uneven flow of molten steel within a mold can be suppressed.

10: Direct drive
11: Euro
20: Connection
30: Discharge
31, 131: Low
131a: Bulkhead
32: Side wall
33: Discharge hole
33aa, 33ba: Outer discharge hole
33ab, 22bb: Inner discharge hole
34: Internal barrier
34a: Top surface
34aa: concave
34aa1: Bottom
34aa2: side
34ae: Single-sided
34b: If you do
34ba: slope
34bb: Horizontal plane
34c: side
35: Branch Euro
36: Distribution Block
36a: Top surface
36b: Distribution Euro
37: Central block
100, 200: Immersion nozzle

Claims (6)

It is an immersion nozzle for continuously casting slabs by discharging molten steel supplied from a tundish into a mold.
The above immersion nozzle has a discharge portion that supplies the molten steel to the mold,
The above immersion nozzle has two regions divided by a thickness direction plane passing through the axis center,
The above discharge part is,
My father,
A side wall extending in the height direction from the outer edge of the above-mentioned lower part
Have,
Four discharge holes are formed in the above discharge portion,
The above discharge holes are arranged in two rows side by side in the width direction in each of the above areas at the bottom of the above discharge section,
The above discharge part is,
An internal barrier is placed in the center of the width direction and distributes the molten steel supplied from the tundish to each of the above areas,
Between the side wall and the inner wall of each of the above areas, a branch flow path through which the molten steel branch distributed by the inner wall flows,
A distribution block that is on the lower side than the above inner barrier and further distributes the above branch flow that has passed through the above branch flow path in each above region to the distribution flow path and supplies it to each above discharge hole.
Have,
In the case where, among the two discharge holes arranged in each of the above regions, the discharge hole arranged on the outer side in the width direction is an outer discharge hole, the discharge hole arranged on the inner side in the width direction is an inner discharge hole, and one of the branch flow paths is blocked, the relationship between the flow rate Qa of the molten steel discharged from the inner discharge hole arranged in the region where the branch flow path is blocked and the flow rate Qb of the molten steel discharged from the inner discharge hole arranged in the region where the branch flow path is not blocked satisfies equation (1),
The relationship between the discharge flow rate Q _out of the molten steel discharged from the outer discharge hole and the discharge flow rate Q _IN of the molten steel discharged from the inner discharge hole satisfies equation (2).
Qa/Qb>1.0 … (1)
0.1≤Q _IN /Q _out ≤1.0 … (2)
An immersion nozzle characterized by: In the first paragraph,
The above immersion nozzle has a direct driving part for receiving the molten steel supplied from the tundish, the discharge part, and a connecting part for connecting the direct driving part and the discharge part.
An immersion nozzle, characterized in that the projection area of the inner barrier when the immersion nozzle is projected on a horizontal plane is greater than the flow path area of the direct driving portion. In paragraph 1 or 2,
An immersion nozzle characterized in that the surface of the inner wall that receives the molten steel supplied from the tundish has a concave portion. In paragraph 1 or 2,
In each of the above regions, the outer discharge angle α1, which is defined from the angle of the wall surface forming the outer discharge hole, is between 40° downward and 75° downward, and the relationship with the inner discharge angle α2, which is defined from the angle of the wall surface forming the inner discharge hole, satisfies equation (3).
-5°≤|α2|-|α1|≤15°… (3)
An immersion nozzle characterized by: In the second paragraph,
An immersion nozzle characterized in that the value of the flow path area of the branch flow path/the flow path area of the direct driving part is 0.4 or more and 1.5 or less. In the second paragraph,
An immersion nozzle characterized in that the value of the flow path area of the above distribution flow path/the flow path area of the above direct driving part is 0.3 or more and 1.5 or less.

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