TWI731561B - Dip the mouth - Google Patents

Abstract

The purpose of the present invention is to stabilize the molten steel ejection flow in the flat dip nozzle, stabilize the molten surface in the mold, that is, reduce its fluctuation. In the present invention, in a flat dip nozzle with a width (Wn) of the inner hole greater than the thickness (Tn) of the inner hole, a lateral protrusion protruding in the thickness direction is provided on the wall surface in the width direction of the flat portion (1). The side protrusions (1) are arranged in pairs at an axisymmetrical position with respect to the longitudinal center axis of the wall surface in the width direction, and are arranged in pairs obliquely in the width direction and downward direction. Furthermore, the side protrusions (1) are in the width direction. The two walls of the direction are opposed to each other.

Description

Dip the mouth

The present invention relates to a dipping nozzle for continuous casting for pouring molten steel from a feeding trough into a mold, and particularly relates to a dipping nozzle used as a dipping nozzle for casting thin flat blanks, medium-thick flat blanks, etc., in the horizontal direction (and the vertical direction). Vertical direction) A dip nozzle with a flat cross-section.

In the continuous casting process where molten steel is continuously cooled and solidified to form cast slabs of a predetermined shape, molten steel is poured into the mold through a continuous casting dipping nozzle (hereinafter also referred to as "dipping nozzle") installed at the bottom of the feed tank .

Generally speaking, the dipping nozzle is composed of a pipe body with a bottom. The upper end of the pipe body becomes a molten steel inlet, and a molten steel flow path (inner hole) extending downward from the molten steel inlet is formed inside. ), on the lower side of the tube body, a pair of discharge holes communicating with the molten steel flow path (inner hole) are formed oppositely. The dipping nozzle is used with its lower part immersed in molten steel in the mold. In this way, it can prevent the molten steel from splashing, and block the contact of molten steel with the atmosphere to prevent oxidation. In addition, by using the dipping nozzle, the molten steel in the mold is rectified, and impurities such as slag and non-metallic inclusions floating on the molten surface are prevented from being caught in the molten steel.

In recent years, in continuous casting, the production of thin flat slabs, medium-thick flat slabs, and other thin cast slabs has increased. In order to correspond to such a thin mold for continuous casting, the dip nozzle must be flat. For example, Patent Document 1 discloses a flat dip nozzle with a discharge hole provided on the short side side wall; Patent Literature 2 discloses a flat dip nozzle with a discharge hole also on the lower end surface. In these flat dipping nozzles, generally, the width of the inner hole is enlarged between the ejection holes from the molten steel introduction port to the mold.

However, in the case of a shape in which the width of the inner hole is enlarged and a flat shape, the flow of molten steel in the dip nozzle is likely to become turbulent, and the discharge flow to the mold is also turbulent. The turbulence of the molten steel flow can also be the cause of the following problems, that is, the fluctuation of the molten steel surface (the molten steel surface) in the mold increases, the powder is drawn into the cast sheet, and the temperature is not uniform. , Poor casting quality, increased risk of operation, etc. Therefore, it is necessary to stabilize the molten steel flow in and out of the dipping nozzle.

In order to stabilize these molten steel flows, for example, Patent Document 3 discloses a dip nozzle in which at least two bending surfaces are formed from a point (center) on a plane below the inner hole toward the lower edge of the discharge hole. facet). Furthermore, this patent document 3 discloses a dip nozzle provided with a splitter that splits the molten steel stream into two streams. Compared with the dipping nozzles that do not have the means to change the flow direction in the internal space like Patent Literature 1 and Patent Literature 2, the flat dip nozzle disclosed in Patent Literature 3, the molten steel flow in the dipping nozzle The stability becomes higher.

However, in the case of such a means of dividing the molten steel flow into the left and right directions, the fluctuation of the molten steel ejection flow between the left and right ejection holes still increases, resulting in large fluctuations of the molten steel level in the mold.

Under the aforementioned background, the inventors of the present invention invented the flat dip nozzle disclosed in Patent Document 4, which contributed to the stabilization of the melt level in the mold. [Prior Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Application Laid-Open No. 11-5145 [Patent Document 2] Japanese Patent Application Laid-Open No. 11-47897 [Patent Document 3] Japanese Special Publication No. 2001-501132 [Patent Document 4] International Publication No. 2017/81934

[The problem to be solved by the invention]

However, the inventors of the present invention found that even with the flat dip nozzle of Patent Document 4, under certain operating conditions, especially in the region where the cross-sectional shape of the inner hole near the upper end of the dip nozzle is circular, the smallest cross-sectional area In continuous casting under conditions such as a molten steel flow rate of approximately 0.04 (t/(min.･cm ² )) or higher based on the position, the effects of stabilization of the molten surface in the mold may still be insufficient.

Therefore, the problem to be solved by the present invention is to provide a dip nozzle that stabilizes the melt level in the mold, that is, reduces its fluctuation in the case of a flat dip nozzle. [Technical means to solve the problem]

The flat dip nozzle in Patent Document 4 is mainly provided with a protrusion in the center of the inner hole. Based on this, in order to fine-tune the discharge flow and shape, it is also provided on the side of the same as the aforementioned center or with a smaller protrusion thickness. Of the protrusion. On the other hand, in the present invention, symmetrical protrusions are provided on the side, and a space without protrusions is formed between the side protrusions, or based on the side protrusions, the protrusion length is longer than the aforementioned side protrusions. The protrusion is a smaller protrusion.

According to the structure of the flat dip nozzle in Patent Document 4, the molten steel flow in the inner hole is induced in a way that the side (referring to the width direction of the flat part of the nozzle, the same below) is greater than the flow in the direction directly below the center. . In this case, there is a tendency to increase the flow rate of molten steel from the spit hole. Under conditions where the flow rate of molten steel per unit time and per unit area is large, the fluctuation of the molten steel level in the mold may increase. situation. On the other hand, according to the structure of the dip nozzle of the present invention, the molten steel flow in the inner hole is adjusted to increase the flow rate directly below the center, thereby inducing the flow rate toward the side to be relatively reduced. In other words, in the present invention, compared to the case of the structure of the dip nozzle of Patent Document 4, the ratio of the flow rate directly below the center/the flow rate toward the side is relatively increased. In addition, as mentioned above, the ratio is basically adjusted in the relationship between the flow rate directly below the center/the flow rate toward the side, and the relationship does not necessarily become the relationship of the flow rate directly below the center>the flow rate toward the side.

In order to obtain the above-mentioned flow form, the present invention is a flat dip nozzle of 1 to 8 below. 1. A dipping nozzle formed in a flat shape with an inner hole having a width Wn greater than a thickness Tn of the inner hole, and provided with a pair of discharge holes at the lower part of the short side side wall, and on the wall surface in the width direction of the flat part, At a position that is axisymmetric with respect to the longitudinal center axis of the wall surface in the width direction, the portions that are inclined in the width direction and the downward direction and protrude in the thickness direction (hereinafter referred to as "side protrusions") are arranged in pairs , The side protrusions are opposed to the two wall surfaces in the width direction, and the thickness of the inner hole at the position where the side protrusions are arranged is set to 1, the total protrusions in the thickness direction of the side protrusions The length Ts is equal to 0.18 or more and 0.90 or less for the two side protrusions of the aforementioned pair. 2. The dipping nozzle according to 1 above, wherein a protrusion (hereinafter referred to as a "central protrusion") is provided on the widthwise wall surface between the pair of two lateral protrusions, and the central protrusion The protrusion length in the thickness direction is the sum of the thickness direction when the thickness of the inner hole at the position where the side protrusion is arranged is set to be smaller than the protrusion length in the thickness direction of the side protrusion The protrusion length Tp is 0.40 or less (excluding 0). 3. The dipping nozzle according to the above 2, wherein the upper end surface of the central protrusion is formed in a horizontal shape in the width direction, a curved shape with the center as the apex, or a shape that includes a curved point and protrudes upward . 4. The dipping nozzle according to any one of 1 to 3 above, wherein the upper end surfaces of the side protrusions and the center protrusions are formed in a horizontal shape toward the center of the inner hole, and downward in a plane or curved surface Inclined shape. 5. The dipping nozzle according to any one of 1 to 4 above, wherein the protruding lengths of either or both of the lateral protrusions and the central protrusions are the same, or oriented toward the width direction A shape in which the center direction of the wall surface is shortened in a straight line, a curve or a segment. 6. The dipping nozzle according to any one of 1 to 5 above, wherein one or both of the side protrusions and the side protrusions provided with the center protrusions are provided in a plurality of Place. 7. The dipping nozzle according to any one of 1 to 6 above, wherein the inner hole has an upward protrusion near the center of the bottom. 8. The dipping nozzle according to any one of 1 to 7 above, wherein the dipping nozzle is an area in which the cross-sectional shape of the inner hole in the vicinity of the upper end of the dipping nozzle is circular, based on the position of the smallest cross-sectional area For continuous casting with a molten steel flow rate of 0.04 (t/(min.･cm ^{2 )) or more.}

In the present invention, the width Wn and thickness Tn of the inner hole refer to the width of the inner hole (length in the longitudinal direction) at the upper end position of the pair of discharge holes provided on the short side side wall of the dip nozzle. ), thickness (length in the short-side direction). [Effects of Invention]

According to the flat dipping nozzle of the present invention, the direction of the molten steel flow is not fixed or completely separated from the central part to the side part, and the molten steel flow can be controlled to a continuous state of increasing and decreasing gradually, which can ensure the immersion nozzle The flow of molten steel within is moderately balanced. In this way, even under certain operating conditions, especially in the area with a circular cross-sectional shape near the upper end of the dip nozzle, based on the minimum cross-sectional area position, the molten steel flow rate is approximately 0.04(t/(min.･cm ²⁾ )) The above conditions are carried out, and in the continuous casting where there is a tendency to generate a high speed or a large amount of molten steel flow on the side of the side spit hole, the flow velocity or flow rate of the molten steel flowing out of the spit hole can still be moderately suppressed , And stabilize the melt level in the mold, which can reduce its fluctuation. Furthermore, since the fluctuation of the melt level in the mold is suppressed, the entrapment of powder and the like in the mold is reduced, and the floating of inclusions in the molten steel can be promoted to improve the quality of the cast slab. In addition, because the excessive molten steel flow to the side wall of the mold can be suppressed, the risk of accidents such as casting leakage can also be reduced.

By providing a shunting means like the aforementioned Patent Document 3, a molten steel flow toward the end side in the width direction can be formed to some extent. However, when the flow is fixed or completely divided like that, each part of the inner hole, that is, each single narrow range, produces a separate molten steel flow, and it is easy to produce parts with different flow directions and flow rates according to the location of the inner hole. Especially when the flow rate and direction are fluctuated by the control of the molten steel flow rate, etc., the molten steel flow may deviate to either direction, and the discharge flow from the dipping nozzle into the mold and the molten surface are obviously disturbed. situation.

Therefore, in the present invention, for example, as shown in the first form of FIG. 1, first, the flat portion of the dip nozzle 10 is provided on the side portion of the wall surface in the width direction (long side): the central axis of the wall surface in the width direction is A pair of axisymmetric side protrusions 1 (refer to FIG. 1(a), etc., hereinafter also simply referred to as "axisymmetric side protrusions"). The upper surface of the pair of side protrusions 1 is inclined from the center side of the side protrusion 1 toward the width direction of the flat portion and the lower direction, that is, the direction of the discharge hole 4. With such an inclination, the flow velocity and flow pattern of the molten steel in the inner hole 3 and from the discharge hole 4 can be stably changed while suppressing the occurrence of eddy currents and the like, and this can be optimized.

The aforementioned pair of axisymmetric side protrusions are also opposed to each other on the other widthwise wall surface of the inner hole in a plane symmetrical relationship with respect to the thickness direction of the flat portion (refer to Figure 1(b), etc., below The side protrusions in the relationship of surface symmetry are also simply referred to as "side protrusions of surface symmetry"). In the present invention, for example, as shown in FIG. 6, if the thickness Tn of the inner hole at the position where the plane-symmetric side protrusion 1 is arranged is set to 1, the total length Ts of the side protrusion 1 in the thickness direction is set Set to 0.18 or more and 0.90 or less. That is, there is a space for the molten steel to pass between the side protrusions that are plane-symmetrical.

By allowing such a spaced space to exist, the molten steel flow in the inner hole is not fixed or completely divided, but the flow direction and flow rate of the part through which the molten steel flow passes are smoothly controlled. In this way, it is possible to alleviate the situation where the molten steel flow flows with a clear boundary on the side of the ejection hole.

In addition, by adjusting the installation location, length, direction, etc. of the side protrusions, the molten steel can be prevented from flowing near the center or concentrated on the side, and it can be moved toward the end side in the width direction, that is, the side of the ejection hole and the center. Side dispersion keeps the molten steel flow in a proper balance. Moreover, not only the dispersion is carried out, but the space is connected in the area where the lateral protrusions are provided. The molten steel flow does not become a completely split state but forms a gentle boundary, which is gently mixed and homogenized to become a dispersed liquid. flow.

Also as described above, the installation location, length, direction, etc. of the side protrusions can be appropriately adjusted. For example, in the second form shown in FIG. 2, in addition to the side protrusion of FIG. 1 (in FIG. 2, the symbol 1a is denoted, and hereinafter also referred to as "lower side protrusion"), an upper side protrusion is also provided. The pair of side protrusions (in FIG. 2, the symbol 1b is indicated, and is also referred to as "upper side protrusion" hereinafter).

Furthermore, in the present invention, between the axisymmetric side protrusions, like the third and fourth forms shown in FIGS. 3 and 4, protrusions with a protrusion length smaller than the aforementioned axisymmetric side protrusions can be provided Department (central protrusion). In the third form shown in Fig. 3, it is projected on the axisymmetric side of Fig. 1 The central protrusion 1p is provided between the exit parts 1 and 1, and in the fourth form shown in FIG. 4, the central protrusion 1p is provided between the axisymmetric lower side protrusions 1a and 1a in FIG.

This structure can obtain the effect of increasing the ratio of the molten steel flow between the aforementioned axially symmetrical side protrusions (central part)/the side molten steel flow, which is the opposite of the effect in Patent Document 4. In Patent Document 4, by providing a protruding portion with a protruding length greater than the aforementioned axisymmetric side protruding portion, compared to the molten steel flow between the aforementioned axisymmetric side protruding portion, the side protruding The molten steel flow increases. In continuous casting with a large molten steel flow rate (approximately 0.04 (t/(min.. cm ² ) or more)), the molten steel flow between the axisymmetric side protrusions (center)/to the side There are many cases where the increase in the ratio of molten steel flow is effective.

In this way, the balance between the molten steel flow toward the center and the sideward molten steel flow can be based on the molten steel flow rate (the molten steel flow rate per unit time and per unit cross-sectional area), the drawing speed, the size and shape of the mold, The nozzle structure, such as the depth of immersion and the area of the ejection hole, are optimized. Specifically, it can be adopted: adjusting the angle of the lateral protrusions in the width direction and the downward direction, the width direction length, the protrusion length, etc., the structure of the central protrusion between the side protrusions without axial symmetry, and the adjustment of the central protrusion The method of protruding height, adjusting the shape of the upper end surface, etc.

Specifically, regarding the protrusion length of the central protrusion, as illustrated in FIG. 6, the protrusion length Tp/2 is set to be smaller than the protrusion length Ts/2 of the side protrusion 1, and the side protrusion will be arranged. When the thickness Tn of the inner hole at the position of the protrusion 1 is set to 1, the total protrusion length Tp becomes 0.40 or less. In other words, it is set as Tp<Ts, and Tp/Tn≦0.40.

In addition, the upper end surface of the central protrusion may be horizontal in the width direction as shown in FIG. 8, or may be formed as a curved surface with the center as the vertex, or a curved surface including a curved point as shown in FIG. 5 and FIG. Shape protruding from above. With such a shape, the flow rate and flow pattern of molten steel can be further changed and optimized.

Furthermore, the upper end surface of the side protrusion or the center protrusion can also be apex with the boundary part of the width direction (long side) wall surface of the flat part of the dip nozzle as shown in Fig. 9 and face the flat part of the dip nozzle. The center direction in the thickness direction, that is, the inner hole center direction (space side), is inclined downward. With such an inclination, the flow rate and flow pattern of molten steel can be further changed and optimized.

Furthermore, the protruding length of the upper end surface of the side protrusion or the central protrusion can be the same as shown in Fig. 10, and can also be directed toward the width direction of the flat portion of the dip nozzle as shown in Figs. 11 to 13 (Long side) The wall surface is inclined so that the center direction becomes shorter. With such an inclination, the flow rate and flow pattern of molten steel can be further changed and optimized.

In a flat dip nozzle, the ejection hole of the side wall on the short side becomes a form that is long and open in the longitudinal direction. In this ejection hole, there may be a part where the ejection flow rate becomes smaller as you go upward, especially In the vicinity of the upper end, the reverse flow phenomenon of inhalation in the dip nozzle is often observed. Therefore, in the present invention, as shown in Figs. 2 and 4, in addition to the aforementioned axisymmetric and plane symmetric lower side protrusions 1a, one or more axisymmetric and plane symmetric side protrusions may be provided above it. Part 1b (upper side protruding part). The upper side protrusion 1b can have the same optimized structure as the aforementioned lower side protrusion 1a.

The upper side protrusion 1b, in particular, suppresses the turbulence of the molten steel flow such as the decrease in the flow velocity above the discharge hole and the reverse flow near the upper end, and supplements the uniformity of the flow velocity distribution at each position in the longitudinal direction of the discharge hole. It also has the function of adjusting the flow balance in the up and down direction. Also between the upper side protrusions 1b and 1b, a center protrusion can be provided in the same manner as between the aforementioned lower side protrusions 1a and 1a.

In addition, the bottom 5 inside the dipping nozzle may have no spit hole formed near the center as shown in FIG. 14, but may be used as the wall surface of the partition wall with the mold, or may be as shown in FIGS. 1 to 5, 7, and 8. As shown in FIG. 15, FIG. 16, etc., the center part is made to protrude upward, and it becomes the structure including the bottom protrusion part. Furthermore, as shown in FIG. 17, the discharge hole 6 may be provided in the bottom part 5. As shown in FIG. The protruding structure of the bottom like this helps to change the flow direction, form, flow rate, etc. of the molten steel flow toward the center of the discharge hole.

Next, the present invention will be explained together with the embodiments.

[Example A] Example A is directed to the second form of the present invention shown in FIG. 2, that is, as the protrusions, two axial and plane symmetrical side protrusions 1a, 1b are provided, between the lower side protrusions 1a, 1a The dipping nozzle of the form without the central protrusion, and the fourth form of the present invention shown in FIG. 4, that is, as the protrusion, the side protrusions 2 sections 1a, 1b are provided with axial symmetry and plane symmetry, and are located below A nozzle with a central protrusion 1p between the side protrusions 1a and 1a, showing the protruding length of the lower side protrusion 1a and the central protrusion 1p in the direction of the inner hole space of the nozzle (a pair of protrusions with plane symmetry) The total length) Ts and Tp relative to the thickness of the inner hole of the dip nozzle (length in the short side direction) Tn ratio Ts/Tn, Tp/Tn, and the degree of change of the melt level in the mold (the drift index in the mold and the melt in the mold) The water model experiment results of the relationship between the height of liquid level fluctuation.

The specifications of the dip nozzle are as follows. ･Full length: 1165mm ･Melting steel import port: φ86mm ･Width of the inner hole at the upper end of the spit hole (Wn): 255mm ･The thickness of the inner hole at the upper end of the spit hole (Tn): 34mm ･The height of the upper end of the spit hole from the lower end of the mouth: 146.5mm ･The height of the central protrusion (the height from the lower end of the mouth): 155mm ･The thickness of the wall of the immersion nozzle: about 25mm ･The thickness of the bottom of the immersion nozzle (the apex of the central part): height 100mm ･Upper side protrusion (1b): The length in the width direction of the nozzle (left and right) is 25mm, Ts/Tn ratio=0.74, The inclination angle to the direction of the discharge hole is 45 degrees, The width direction and thickness direction of the dipping nozzle on the upper end surface are horizontal, The distance between the side protrusions is 100mm, No central protrusion ･Lower side protrusions (1a): The length in the width direction of the nozzle (left and right) is 40mm, Ts/Tn ratio=0.1~1.0 (no space), The inclination angle to the direction of the discharge hole is 45 degrees, The width direction and thickness direction of the dipping nozzle on the upper end surface are horizontal, Between the side protrusions is 60mm, Central protrusion Tp/Tn ratio = 0 (none) ~ 0.7

The conditions of the mold and fluid are as follows. ･Width of the mold: 1650mm ･Thickness of the mold: 65mm (185mm at the upper end of the center) ･Dip depth (from the top of the discharge hole to the water surface): 83mm ･Supply rate of fluid: 0.065t/(min･cm ² ) ※Converted to melting Steel value

Here, the drift index in the mold is set to 1.0 when there is no drift, and the evaluation criteria are set as: 0.8≦the drift index in the mold≦1.2, and the molten surface fluctuation height in the mold (mm)≦15mm is regarded as a solution to the present invention The effect of the problem. In addition, the drift index in the mold refers to the flow rate of the set melt surface (30mm in the water from the upper end surface of the set water level) on the left and right sides of the ejection hole of the dipping nozzle in the mold measured by a water model experiment, and the above-mentioned left and right flow rates are expressed as a ratio. The absolute value of the time, that is, the value of left flow rate/right flow rate (or right flow rate/left flow rate), and the height of melt level fluctuation in the mold refers to the maximum value of Sw in FIG. 18.

The results are shown in Table 1.

The deviation index in the mold and the height of the molten surface fluctuation in the mold, as for the side protrusions, show that the Ts ratio (Ts/Tn) to Tn is 0.18 or more and 0.90 or less, which can meet the standard. In addition, regarding the case where the central protrusion is provided, it can be seen that when the protrusion length is smaller than the protrusion length of the lateral protrusion (Tp<Ts), and the Tp ratio to Tn (Tp/Tn) is 0.4 or less, Can meet the benchmark.

[Example B] Example B shows the results of the following water model experiment. That is, in the fourth form of the present invention shown in FIG. 4, the upper end surfaces of the lower lateral protrusion 1a and the central protrusion 1p are formed as shown in FIG. 9 This is the degree of variation of the molten surface in the mold when the plane is inclined downward in the direction of the inner hole center.

Here, set the Ts/Tn ratio of the lower lateral projection=0.74, and the Tp/Tn ratio of the central projection=0.18, and the inclination angle of the lower lateral projection and the central projection in the direction of the inner hole (Figure 9 Compare the case where θ) is 0 degrees (horizontal) and the case of 45 degrees. The other conditions are the same as in Example A.

The result is shown in Figure 19. The vertical axis of FIG. 19 is a value obtained by averaging the maximum melt surface fluctuation value Sw (mm) in the left-right direction of the ejection hole when the inclination angle θ is either 0 degrees or 45 degrees.

As shown in Fig. 19, it can be seen that when the inclination angle θ is either 0 degrees or 45 degrees, it becomes a value significantly smaller than the reference 15mm, and furthermore, it is 2.0 (mm) at 45 degrees, which is reduced to 0 degrees. The case is about 1/2 of 3.75 (mm).

10: Dipping mouth 1: Side protrusion 1a: Lower side protrusion 1b: Upper side protrusion 1p: central protrusion 2: molten steel inlet 3: Inner hole (melting steel flow path) 4: Discharge hole (wall side on the short side) 5: bottom 6: Spit hole (bottom) 7: Melt level 20: Mold Wn: The width of the inner hole of the dipping nozzle (the length in the long side direction) Wp: The width between the two ends of the side protrusion Wc: The width of the central protrusion Tn: The thickness of the inner hole of the dipping nozzle (length in the short side direction) Ts: The protruding length of the side protrusion in the spatial direction (the total length of a pair) Tp: The protruding length of the central protrusion in the spatial direction (the total length of a pair) ML: Mold width (long side) Ms: Mold thickness (short side, side) Mc: mold thickness (short side, center) Sw: The degree of variation of the melt level in the mold (the size between the upper end and the lower end)

[Figure 1] is a schematic diagram showing an example of the dip nozzle of the present invention provided with side protrusions (the first form of the present invention), Figure 1 (a) is a cross-sectional view through the center of the short side, Figure 1 (b) ) Is a cross-sectional view (view AA) through the center of the long side. [Fig. 2] is a schematic diagram showing an example of the dip nozzle of the present invention (the second form of the present invention) provided with a pair of side protrusions in addition to the side protrusions of Fig. 1, Fig. 2(a ) Is a cross-sectional view through the center of the short side, and Figure 2(b) is a cross-sectional view (view AA) through the center of the long side. [Fig. 3] A schematic diagram showing an example of the dip nozzle of the present invention (the third aspect of the present invention) in which a central protrusion is provided between the side protrusions in Fig. 1, and Fig. 3(a) passes through the center of the short side Figure 3(b) is a cross-sectional view through the center of the long side (view AA). [FIG. 4] In addition to the side protrusions and the central protrusion between the side protrusions in FIG. 3, an example of the dip nozzle of the present invention is provided with a pair of side protrusions on the upper side (the first of the present invention). Fig. 4(a) is a cross-sectional view through the center of the short side, and Fig. 4(b) is a cross-sectional view (view AA) through the center of the long side. [Figure 5] is an enlarged view of the vicinity of the part where the central projection is provided between the side projections in Figure 3 or Figure 4, the central part of the central projection is the central part of the bottom projection which is linearly formed in a mountain shape in the upward direction This is an example where the mountain shape is formed linearly in the upward direction, and it is a cross-sectional view passing through the center of the short side. [Fig. 6] is a plan view of the inner hole of the dipping nozzle of Fig. 5, which is a schematic diagram showing the relationship between the lateral protrusions and the central protrusion. [Fig. 7] is an example of the upper end of the central protrusion in Fig. 5 being a curved surface, and is a schematic diagram showing a cross-section passing through the center of the short side of the dipping nozzle. [Fig. 8] is an example in which the upper end of the central protrusion in Fig. 5 is flat, and is a schematic diagram showing a cross-section passing through the center of the short side of the dip nozzle. [Fig. 9] An example of a shape in which the upper surface of the side protrusion or the central protrusion is inclined toward the center of the inner hole, and is a schematic diagram showing a cross section passing through the center of the long side of the dipping nozzle. Fig. 10 is an example in which the protruding length of each upper surface of the side protrusion and the center protrusion of Fig. 5 is constant (the end of the inner hole is parallel to the wall surface in the width direction), and is a schematic plan view. Fig. 11 is an example in which the protruding length of the upper surface of the central protruding portion of Fig. 5 is linearly shortened in the central direction, and is a schematic plan view. Fig. 12 is an example in which the protruding length of the upper surface of the central protruding portion of Fig. 5 is curvilinearly shortened toward the center, and is a schematic plan view. Fig. 13 is an example in which the protruding lengths of the upper surfaces of the side protrusions and the center protrusions of Fig. 5 are linearly and integratedly continuously shortened, and are schematic plan views. [Fig. 14] is an example in which the upper surface of the bottom protrusion of the dip nozzle of Fig. 5 is flat, and is a schematic diagram showing a cross section passing through the center of the short side. [Fig. 15] It is an example of the upper surface of the bottom protrusion of the dipping nozzle in Fig. 5 being a curved surface, and is a schematic diagram showing a cross section passing through the center of the short side. Fig. 16 is an example in which the upper surface of the bottom protrusion of the dip nozzle of Fig. 5 is provided with a convex portion in the center and has a diameter enlarged toward the bottom. [Fig. 17] is an example showing that the bottom protrusion of the dip nozzle of Fig. 5 is also provided with a hole for discharging molten steel, and is a schematic diagram showing a cross section passing through the center of the short side. [Figure 18] is a schematic diagram showing the mold and the change of the molten steel surface (melting steel surface) in the mold, Figure 18 (a) is a schematic plan view of the vicinity of the molten metal surface (inner surface) of the mold, and Figure 18 (b) is through A schematic view of a cross-sectional view (half in the longitudinal direction) of the center of the short side near the molten surface of the mold (inner surface). Fig. 19 is a graph showing the variation (maximum value, left and right average) of the melt surface (melting steel surface) in the mold of Example 3 in Table 1.

1: Side protrusion

2: molten steel inlet

3: Inner hole (melting steel flow path)

4: Discharge hole (wall side on the short side)

5: bottom

10: Dipping mouth

Claims (8)

A dipping nozzle formed in a flat shape with an inner hole having a width (Wn) greater than the thickness (Tn) of the inner hole, and a pair of discharge holes are provided at the lower part of the short side side wall, and the wall surface in the width direction of the flat part Above, at a position that is axisymmetric with respect to the longitudinal center axis of the wall surface in the width direction, a pair of parts that are inclined in the width direction and the lower direction and protrude in the thickness direction (hereinafter referred to as "side protrusions") are paired When the thickness of the inner hole at the position where the lateral projections are arranged is set to 1 when the lateral projections are opposed to the two wall surfaces in the width direction, the lateral projections are in the thickness direction of the lateral projections. The total protrusion length (Ts) is equal to 0.18 or more and 0.90 or less for the two side protrusions in the aforementioned pair. The dipping nozzle according to claim 1, wherein a protrusion (hereinafter referred to as a "central protrusion") is provided on the widthwise wall surface between the pair of two lateral protrusions, and one of the central protrusions The protrusion length in the thickness direction is smaller than the protrusion length in the thickness direction of the side protrusion, and the total protrusion in the thickness direction when the thickness of the inner hole at the position where the side protrusion is arranged is set to 1 The length (Tp) is 0.40 or less (excluding 0). The dipping nozzle according to claim 2, wherein the upper end surface of the central protrusion is formed in a horizontal shape in the width direction, a curved shape with the center as a vertex, or a shape that includes a curved point and protrudes upward. The dipping nozzle according to any one of claims 1 to 3, wherein the upper end surfaces of the side protrusions and the center protrusions are formed in a horizontal shape toward the center of the inner hole and inclined downward on a flat surface or a curved surface shape. The dipping nozzle according to any one of claims 1 to 3, wherein the protruding lengths of either or both of the side protrusions and the center protrusions are respectively the same or facing the wall surface in the width direction A shape that is straight or curvilinear in the center direction or shortened in segments. The dipping nozzle according to any one of claims 1 to 3, wherein any one or both of the side protrusions and the side protrusions provided with the center protrusions are provided in a plurality of places in the vertical direction . The dipping nozzle according to any one of claims 1 to 3, wherein a protrusion in an upward direction is provided near the center of the bottom of the inner hole. The dipping nozzle according to any one of claims 1 to 3, wherein the dipping nozzle is an area where the cross-sectional shape of the inner hole in the vicinity of the upper end of the dipping nozzle is circular, and the melting is based on the position of the smallest cross-sectional area. For continuous casting with steel flow rate above 0.04 (t/(min.. cm ^{2 )).}

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