TW202035036A - Immersion nozzle - Google Patents

Abstract

The objective of the present invention is to stabilize a discharge flow of molten steel and stabilize the melt surface inside a mold, that is, to reduce fluctuation thereof, in a flat immersion nozzle. In the present invention, lateral protrusion parts 1 protruding in the thickness direction are provided in the wall surface in the width direction of a flat portion in an immersion nozzle, which has a flat shape in which the width Wn of an inner hole is greater than the thickness Tn of the inner hole. These lateral protrusion parts 1 are arranged so as to form a pair slanting in the width direction and downward, at axisymmetric positions with respect to center axis in the vertical direction of the wall surface in the width direction, and the lateral protrusion parts 1 are arranged facing each other in both wall surfaces in the width direction.

Description

Dip

The present invention relates to a dipping nozzle for continuous casting for pouring molten steel from a feeding trough into a mold, and particularly to a dipping nozzle used for casting thin flat blanks, medium-thick flat blanks, etc., in the lateral 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 dip nozzle (hereinafter also referred to as "dip 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 pipe 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, etc., 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 dipping nozzle with a discharge hole provided on the short side side wall; and Patent Document 2 discloses a flat dipping nozzle with a discharge hole also provided on the lower end surface. In these flat dip nozzles, in general, the width of the inner hole is enlarged between the ejection holes from the molten steel inlet 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 easily 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 quality of cast slab, increased risk of operation, etc. Therefore, it is necessary to stabilize the molten steel flow in and out of the dip 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 for splitting 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 splitting the molten steel flow in the left and right directions, there is still a case where the fluctuation of the molten steel discharge flow between the left and right discharge holes becomes larger, resulting in larger 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 molten surface 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 Publication 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 area where the cross-sectional shape of the inner hole near the upper end of the dip nozzle is circular, the minimum 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 stabilizing 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 or the protrusion thickness is smaller. Of the protrusion. In contrast, 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 such as a large molten steel flow rate per unit time and per unit area, 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 flow of molten steel in the inner hole is adjusted to increase the flow directly below the center, and thereby the flow to the side is relatively reduced for induction. In other words, in the present invention, compared with 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 toward the center directly below>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 dip 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 "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 on a flat surface or a 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 side protrusions and the center 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 any one or both of the side protrusions and the side protrusions provided with the central protrusions are provided in plural in the vertical direction Place. 7. The dipping nozzle according to any one of 1 to 6 above, wherein the inner hole has an upward protrusion near the bottom center. 8. The dipping nozzle according to any one of 1 to 7 above, 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 minimum cross-sectional area position is used as a reference 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 Moderate balance of molten steel flow inside. 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 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 rate or flow rate of the molten steel flowing out of the spit hole can 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, since 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 stream toward the end 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 may be significantly 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 molten steel in the inner hole 3 and from the ejection hole 4 can be steadily changed while suppressing the occurrence of eddy currents and the like, and can be optimized.

The aforementioned pair of axisymmetric side protrusions are also opposed to the width direction wall surface of the other side of the inner hole in a plane symmetric 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-symmetrical side protrusion 1 is arranged is set to 1, then 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 through between the side protrusions that are surface symmetric. 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 gently 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 discharge 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 discharge hole side 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, and 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 protrusions of FIG. 1 (in FIG. 2, the symbol 1a is denoted, and hereinafter also referred to as "lower side protrusions"), an upper part 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" below).

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, a central protrusion 1p is provided between the axisymmetric side protrusions 1 and 1 in FIG. 1, and the fourth form shown in FIG. 4 is axisymmetric in FIG. 2 A central protrusion 1p is provided between the lower side protrusions 1a and 1a.

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 larger than the aforementioned axisymmetric side protruding portion, compared to the molten steel flow between the aforementioned axisymmetric side protruding portion, the side 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 (central part)/to the side There are many cases where the reduction of 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, 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 discharge hole, are optimized. Specifically, it is possible to use: adjust the angle of the lateral protrusions in the width direction to the downward direction, the width direction length, the protrusion length, etc., to form a central protrusion between the side protrusions without axisymmetric structure, and adjust the central protrusion Methods 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 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 to 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 apex, or a curved surface including a curved point as shown in FIG. 5 and FIG. Shape protruding from above. With this 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 central 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. The center direction in the thickness direction, that is, the inner hole center direction (space side), is inclined downward. With this 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 lateral 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 this inclination, the flow rate and flow pattern of molten steel can be further changed and optimized.

In a flat dip nozzle, the discharge hole of the side wall on the short side becomes a form that is long and open in the longitudinal direction. In this discharge hole, there may be a part where the discharge 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 can be provided above it. Section 1b (upper side protrusion). 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 similarly to the aforementioned lower side protrusions 1a and 1a.

In addition, the bottom 5 inside the dipping nozzle may not have a spit hole formed near the center as shown in Fig. 14, but only serve as the wall surface of the partition wall with the mold, or it 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. 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 when it changes to the direction of the ejection hole.

Next, the present invention will be described together with 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 axially symmetrical 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. 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 a plane symmetry The total length of 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 variation 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 wall thickness 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 dip nozzle on the upper end surface are horizontal, 100mm between the side protrusions, No central protrusion ･Lower side protrusion (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 end of the discharge hole to the water surface): 83mm ･The fluid supply speed: 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 criterion is set as: 0.8≦the drift index in the mold≦1.2, and the molten surface variation height in the mold (mm)≦15mm is regarded as the solution to the present invention The effect of the problem. In addition, the drift index in the mold refers to the flow velocity 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 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 melt level fluctuation in the mold, as for the lateral 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 side protrusion=0.74, and the Tp/Tn ratio of the center protrusion=0.18, and the inclination angle of the lower side protrusion and the center protrusion 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. About 1/2 of 3.75 (mm) of the case.

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 (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 protrusions 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 and lower ends)

[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 sectional view (view AA) through the center of the long side. [Figure 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, Figure 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] is 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 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 above it (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 (AA view) 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 that is linearly formed in a mountain shape in the upward direction It is an example of forming a mountain shape linearly in the upward direction, and 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 a curved surface at the upper end of the central protrusion in Fig. 5, and is a schematic diagram showing a cross section passing through the center of the short side of the dip 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 dip 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 toward the center, 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 lateral protrusions and the central 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 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 of Fig. 5 being a curved surface. 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, and is a schematic diagram showing a cross section passing through the center of the short side. [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 change of the mold and the molten steel surface (melting steel surface) in the mold, Figure 18 (a) is a schematic plan view of the vicinity of the molten 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 (inner surface) of the mold. Fig. 19 is a graph showing the variation (maximum value, left and right average) of the molten steel 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 on the lower part of the short side wall, On the wall surface in the width direction of the flat portion, at a position that is axisymmetric with respect to the longitudinal center axis of the wall surface in the width direction, a portion that is inclined in the width direction and the downward direction and protrudes in the thickness direction (hereinafter referred to as " Side protrusions") are arranged in pairs, The side protrusions are opposed to both wall surfaces in the width direction, When the thickness of the inner hole at the position where the side protrusions are arranged is set to 1, the total protrusion length (Ts) of the thickness direction of the side protrusions is 0.18 for the two side protrusions in the pair. Above 0.90 and the same. The dipping mouth as described in claim 1, wherein: A protrusion (hereinafter referred to as "central protrusion") is provided on the wall surface in the width direction between the pair of two lateral protrusions, and the protrusion length in the thickness direction of the central protrusion is longer than the lateral protrusion The protrusion length in the thickness direction of the part is smaller, and when the thickness of the inner hole at the position where the lateral protrusion is arranged is set to 1, the total protrusion length in the thickness direction (Tp) is 0.40 or less (not including 0) . The dipping mouth as described in claim 2, in which, 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 an apex, or a shape protruding upward including a bending point. 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 a shape inclined downward on a flat surface or a curved surface. The dipping nozzle according to any one of claims 1 to 4, wherein: The protruding lengths of either or both of the side protrusions and the center protrusions are respectively the same, or have a shape that is shortened linearly or curvilinearly or segmentally toward the center direction of the wall surface in the width direction. The dipping nozzle according to any one of claims 1 to 5, wherein: Either 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 6, wherein: There is an upward protrusion near the center of the bottom of the inner hole. The dipping nozzle according to any one of claims 1 to 7, 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 a steel flow rate of 0.04 (t/(min.･cm ² )) or more.

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