JP2009178748A - Stepped immersed nozzle with hand drum shape weir - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an immersed nozzle capable of further reducing a drift current. <P>SOLUTION: A first flow regulating protruding portion 4 extending in parallel to a direction of drilling a molten steel discharging hole 2 is provided on an inner bottom surface 3. The first flow regulating protruding portion 4 is tapered at the center of its extending direction. A pair of second flow regulating protruding portions 8 extending in parallel to the first flow regulating protruding portion 4 and opposing to each other with the first flow regulating protruding portion 4 sandwiched in viewing the bottom surface of the immersed nozzle 1 are provided on an inner circumferential surface 7 of the immersed nozzle 1. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an immersion nozzle used for continuous casting, and more particularly to a technique for reducing the drift of molten steel discharge flow.

(In the present specification, “diffused flow” means at least one or both of a drift of the molten steel discharge flow in the mold thickness direction and a drift of the molten steel discharge flow in the mold width direction.)

  Patent Document 1 (Japanese Patent Application Laid-Open No. 2007-216271) relating to the application of the present applicant discloses an immersion nozzle in which a protrusion extending in parallel with the drilling direction of the molten steel discharge hole is provided on the inner bottom surface (see FIG. 1). 2). And it is described that the drift in the mold thickness direction is reduced by the presence of the protrusions (see FIGS. 10 and 11 in the literature).

  Patent Document 2 (International Publication No. WO 2005/070589 Pamphlet) discloses an immersion nozzle in which one ridge-like protrusion extending in parallel with the discharge direction is provided on the inner surface of the nozzle bottom (see FIG. 2 of FIG. 2). 10 and FIG. 11). According to this ridge-like protrusion, a stable vortex flow toward two opposing discharge holes is formed in each of two regions divided by the ridge-like protrusion, and the discharge flow is stabilized.

  Further, Patent Document 3 (Japanese Patent Laid-Open No. 2005-297022) discloses an immersion nozzle in which four protrusions are arranged in three stages on a surface perpendicular to the molten steel distribution direction, for a total of 12 (see FIG. (See the same document, page 8, lines 5-7, FIG. 2 (A)). Further, it is preferable that an independent protrusion (FIG. 2 (A)) is more preferable with respect to the rectifying effect than an annular protrusion (see FIG. 2 (B)) continuous on one surface perpendicular to the molten steel flow direction. Are listed.

  The immersion nozzles described in Patent Documents 1 to 3 are all excellent, but there is still room for improvement in drift.

  This invention is made | formed in view of such various points, The main objective is to provide the immersion nozzle in which the drift was further reduced.

Means and effects for solving the problems

  The problems to be solved by the present invention are as described above, and the inventors of the present application have made extensive research and, in an immersion nozzle as described in Patent Document 1, a protrusion that extends in the drilling direction of the molten steel discharge hole. By narrowing the center of the mold and providing an appropriate protrusion on the inner peripheral surface that extends parallel to this protrusion, it is possible to reduce drift in the mold width direction and to further reduce drift in the mold thickness direction. (See FIG. 2 of this application, Table 1 of this application).

  Going back to Patent Document 1, Patent Document 1 does not describe or suggest the constricted shape. The same applies to Patent Document 2. Regarding Patent Document 3, although there are references to a large number of scattered protrusions and annular protrusions, there is no description or suggestion about a configuration extending in parallel with the protrusions.

  The applicant of the present application has already filed an application for the technical idea of reducing the drift in the mold width direction by constricting the center of the protrusion extending in the drilling direction of the molten steel discharge hole (Japanese Patent Application No. 2006-355978, Hereinafter referred to as Patent Application 1.) The technical positioning of the present application with respect to this patent application 1 is to achieve a high level of reduction of the drift in the mold thickness direction in addition to the drift reduction effect in the mold width direction achieved by the technical idea disclosed in the patent application 1. It is in.

  Next, means for solving this problem and effects thereof will be described.

  According to the viewpoint of this invention, the immersion nozzle comprised as follows is provided. That is, a pair of opposed molten steel discharge holes are drilled in the peripheral wall of the immersion nozzle at a position away from the inner bottom surface of the immersion nozzle by a predetermined distance. The inner bottom surface of the immersion nozzle is provided with a first rectifying protrusion that extends parallel to the drilling direction of the molten steel discharge hole. The first straightening protrusion is narrowed at the center in the extending direction. A pair of second rectifying protrusions that extend in parallel with the first rectifying protrusion and are opposed to each other with the first rectifying protrusion in the bottom view of the immersion nozzle are provided on the inner peripheral surface of the immersion nozzle. . Each of the second rectifying protrusions is disposed below the first rectifying surface so as to form a pair with the first rectifying surface that is inclined downward toward the axial center side of the immersion nozzle. And a second rectifying surface that is inclined upward toward the axial center side of the immersion nozzle. The inner diameter of the immersion nozzle is set to Dsn, the distance between the lower end of the inner peripheral opening edge of the molten steel discharge hole and the inner bottom surface is set to H, and the top surface of the first rectifying protrusion is viewed from the bottom of the immersion nozzle. A width at the end of the first rectifying protrusion in the extending direction, and a width of the upper surface of the first rectifying protrusion in the bottom view of the immersion nozzle, the first rectifying protrusion The width in the center of the extending direction is b, the protruding height of the first rectifying protrusion is h, the distance between the second rectifying protrusion and the inner bottom surface is e, and the axis of the immersion nozzle The height of the second rectifying protrusion in the direction is f, the thickness of the second rectifying protrusion in the radial direction of the immersion nozzle is g, and the inclination angle of the first rectifying surface with respect to the axis of the immersion nozzle is θ1 is set, and the inclination angle of the second rectifying surface with respect to the axis of the immersion nozzle is θ2. Then, the following formulas (1) to (8) are satisfied.

  According to the above configuration, it is possible to simultaneously realize a reduction in drift in the mold width direction and a reduction in drift in the mold thickness direction at a high level.

  Hereinafter, the configuration of an immersion nozzle according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a perspective view of an immersion nozzle according to an embodiment of the present invention. The immersion nozzle 1 shown in this figure is used for pouring molten steel held in a tundish into a mold, and is formed in a bottomed cylindrical shape.

  FIG. 2 is a partially cutaway perspective view of an immersion nozzle according to an embodiment of the present invention. As shown in this figure, a pair of opposed molten steel discharge holes 2 are drilled in the peripheral wall of the immersion nozzle 1 at a position slightly away from the inner bottom surface 3 of the immersion nozzle 1. And the 1st rectification | straightening protrusion 4 extended in parallel with the piercing | piercing direction of the molten steel discharge hole 2 is provided in the inner bottom face 3 of the immersion nozzle 1. As shown in FIG. The first rectifying protrusion 4 is narrowed at the center in the extending direction. In short, the first rectifying protrusion 4 has a drum shape narrowed toward the center in the extending direction. Further, as shown in the figure, the inner peripheral surface 7 of the immersion nozzle 1 extends in parallel with the first rectifying protrusion 4 and faces the first rectifying protrusion 4 with the first rectifying protrusion 4 being sandwiched in the bottom view of the immersion nozzle 1. A pair of second rectifying protrusions 8 are provided.

  In general, the discharge flow of the molten steel discharged from the molten steel discharge hole 2 of the immersion nozzle 1 and the width direction and thickness direction of the mold are technically closely related. The mold thickness direction is specifically shown. As shown in FIG. 2, the immersion nozzle 1 is generally arranged in the mold so that the drilling direction of the molten steel discharge hole 2 coincides with the mold width direction. 1 and 2 also show the axial direction of the immersion nozzle 1 that is orthogonal to both the mold width direction and the mold thickness direction.

  Please refer to FIGS. FIG. 3 is a front partial sectional view of an immersion nozzle according to an embodiment of the present invention. FIG. 4 is a side partial sectional view of an immersion nozzle according to an embodiment of the present invention. 5 is a cross-sectional view taken along line VV in FIG. Each section shown in FIGS. 3 and 4 includes the axis of the immersion nozzle 1.

(Immersion nozzle 1)
As shown in each figure, the immersion nozzle 1 has a bottomed cylindrical shape having an inner diameter Dsn, and is integrally formed of a refractory together with the first rectifying protrusion 4 and the second rectifying protrusion 8.

(Molten steel discharge hole 2)
The molten steel discharge hole 2 is inclined slightly obliquely downward from the inner periphery to the outer periphery of the immersion nozzle 1 as shown in FIG. 4, and the inner peripheral surface 7 of the immersion nozzle 1 is rounded as shown in FIG. Similarly, the outer peripheral surface 11 of the immersion nozzle 1 has a rounded rectangular outline (see also FIG. 1). Moreover, the molten steel discharge hole 2 is formed so that it may become wide gradually from the inner periphery to the outer periphery of the immersion nozzle 1, as shown in FIG. Here, in FIG. 3, the distance between the lower end 12 b of the inner peripheral side opening edge 12 of the molten steel discharge hole 2 and the inner bottom surface 3 is considered by the symbol H. In general, the space conceived by the symbol H is called a hot water reservoir, and mainly has a function of preventing the molten steel from scattering at the start of casting. The downward discharge angle θt [deg. Deg.] Of the molten steel discharge hole 2 shown in FIG. ] Is preferably about 10 to 55.

(First straightening protrusion 4)
3 and 4 shows only the boundary between the first rectifying protrusion 4 and the other part. <Length> As shown in FIG. 4, the first straightening protrusion 4 extends sufficiently on the inner bottom surface 3 so that both ends thereof are connected to the inner peripheral surface 7, that is, the first straightening protrusion. The extending length of the part 4 is equal to the inner diameter Dsn of the immersion nozzle 1. <Protrusion Height> The protrusion height of the first rectifying protrusion 4 identified by the symbol h in the figure is equal to the distance H which is the height of the hot water reservoir described above. That is, in this embodiment, the relationship h = H is established. <Cross Section> As shown in FIG. 3, the cross section perpendicular to the length of the first rectifying protrusion 4 is substantially trapezoidal and is narrowed in a direction away from the inner bottom surface 3. The side surface of the first rectifying protrusion 4 in this figure is inclined at approximately 60 to 85 ° with respect to the inner bottom surface 3. <Constriction Shape> As shown in FIG. 5, the first rectifying protrusion 4 that is constricted in the center in the extending direction is smoothly constricted in a V shape toward the center in the extending direction. The symbol a is the width of the upper surface 4a of the first rectifying protrusion 4 in the bottom view of the immersion nozzle 1, and indicates the width of the end of the first rectifying protrusion 4 in the extending direction. The symbol b is the width of the upper surface 4 a of the first rectifying protrusion 4 in the bottom view of the immersion nozzle 1, and indicates the width at the center of the extending direction of the first rectifying protrusion 4. And in this embodiment, the 1st rectification protrusion 4 satisfy | fills following formula (1)-(3).

(Second straightening protrusion 8)
3 and 5 indicates only the boundary between the second rectifying protrusion 8 and other portions. <Cross section> As shown in FIG. 3, the cross section perpendicular to the length of the second rectifying protrusion 8 is substantially trapezoidal. It is gradually narrowed as it goes to. That is, the second rectifying protrusion 8 is disposed below the first rectifying surface 13 so as to form a pair with the first rectifying surface 13 as a plane inclined downward toward the axial center side. And a second rectifying surface 14 as a plane inclined upward in the axial direction. Reference sign θ1 represents an inclination angle of the first rectifying surface 13 with respect to the axis. The symbol θ2 indicates the inclination angle of the second rectifying surface 14 with respect to the axis. The side surface 15 of the second rectifying protrusion 8 is a flat surface and is orthogonal to the mold thickness direction. <Height> The symbol f indicates the height of the second rectifying protrusion 8 in the axial direction. Specifically, the height of the second rectifying protrusion 8 including the first rectifying surface 13 and the second rectifying surface 14. Indicates. <Thickness> The symbol g indicates the thickness of the second rectifying protrusion 8 in the mold thickness direction (the mold thickness direction corresponds to one of the radial directions of the immersion nozzle 1), and details are shown in FIG. This is the thickness of the two rectifying protrusions 8, that is, the maximum value of the thickness of the second rectifying protrusion 8. <Others> The symbol e indicates the distance between the second rectifying protrusion 8 and the inner bottom surface 3, and more specifically, between the lower end 14 a of the second rectifying surface 14 of the second rectifying protrusion 8 and the inner bottom surface 3. Indicates the distance. And in this embodiment, the 2nd rectification protrusion 8 satisfy | fills following formula (4)-(8).

  The configuration of the immersion nozzle 1 according to this embodiment has been described above. In addition, from various viewpoints, it is preferable that the surface and the surface intersect at an obtuse angle, and a portion where the surface and the surface intersect with each other is appropriately rounded.

  Next, a unique flow of molten steel realized by employing the above immersion nozzle 1 will be described with reference to FIGS. FIG. 6 is a diagram illustrating the flow of molten steel when a conventional immersion nozzle is used. FIG. 7 is a diagram illustrating the flow of molten steel when the immersion nozzle according to an embodiment of the present invention is used. 6 and 7, a front cross-sectional view, a side cross-sectional view, and a plan cross-sectional view are drawn side by side so that the flow of molten steel can be considered three-dimensionally. In order to emphasize technical differences in the flow of molten steel, it should be understood in advance that the flow depicted in each figure may differ from the actual one in terms of quantitative aspects.

<FIG. 6: Flow of Molten Steel Using Conventional (Patent Document 1) Immersion Nozzle>
When the immersion nozzle described in the above-mentioned Patent Document 1 is adopted, a pair of vortex flows are formed sandwiching a protrusion extending in the center of the inner bottom surface, as shown in FIGS. The However, as shown in FIG. 4B, the pair of vortex flows are not restrained at all in the mold width direction, so that the base point of each vortex flow freely moves along the length of the protrusion.

<FIG. 7: Flow of Molten Steel When Using the Immersion Nozzle According to the Embodiment>
On the other hand, when the immersion nozzle according to the embodiment is employed, the pair of vortex flows are engaged with the narrowed shape of the first rectifying protrusion, as shown in FIG. Restrained in the mold width direction, the vortex base point cannot move along the length of the first rectifying protrusion, thereby reducing the drift in the mold width direction. Further, as shown in FIGS. 4A and 4B, the pair of vortex flows are compressed with a small diameter between the first rectifying protrusion and the second rectifying protrusion arranged in parallel to each other. Formed in the form. As a result, the pair of vortices continue to exist more stably, and therefore, the reduction of the drift in the mold thickness direction achieved by forming the pair of vortices is realized at a high level.

  Hereinafter, a test for confirming the technical effect of the immersion nozzle according to the embodiment will be described. Each numerical range mentioned above is reasonably supported by the following test.

≪Examination: Outline of examination≫
Each test is a so-called water model test that employs a water tank and water instead of a mold and molten steel. Each test was performed while making minor changes to the structure of the immersion nozzle and the size of the mold. For detailed setting values such as the structure of the immersion nozzle and the size of the mold, see Table 1 described later. The immersion nozzle employed in each test was evaluated from multiple points of view. That is, the test for evaluating the drift shown in FIG. 8 and the test for evaluating the water surface flow velocity shown in FIG.

≪Test: First evaluation test: Fig. 8≫
In this test, in a steady state in which water is supplied to the immersion nozzle at a predetermined water flow rate Wat [L / min], the flow velocity of water at points A to D illustrated by bold circles is measured for 100 seconds with an electromagnetic anemometer ( (Model number: VM-806H). Then, the drift Thh [m / s] in the mold thickness direction is determined according to the following formula (9), and the drift Wih [m / s] in the mold width direction is determined according to the following formula (10). Then, a drift degree TW [m / s] defined by the following formula (11) is obtained.

However, in the above formulas (9) and (10), T ₁ means an arbitrary measurement start time, ΔT is 100 seconds, and v _X (t) is a measurement result of the flow rate of water at the point X (however, Discrete data).

  When the relationship of the following formula (12) is satisfied, the corresponding test is evaluated as “◯ (no breakout risk)”, and when not satisfied, it is evaluated as “× (breakout risk)”. I decided to. The basis for the evaluation threshold in the following formula (12) is attached to the end of this specification.

  In addition, the unit of the numerical value in FIG. 8 is mm.

≪Test: Second evaluation test: Fig. 9≫
In this test, in a steady state where water is supplied to the immersion nozzle at a predetermined water flow rate Wat [L / min], the flow rate of water at points E to F illustrated in bold circles for 10 minutes is a first evaluation test. Measure every 1 second using the same electromagnetic velocimeter used in. The measurement result of water flow rate at point E (discrete data) is divided every 10 seconds, the average value in each division is obtained, and the maximum average value among the 60 average values is selected. The same applies to the point F. Then, a “water surface velocity v _m [m / s]” defined by the larger one of the maximum average value selected at the point E and the maximum average value selected at the point F is obtained, and the following formula (13 ) If the condition is satisfied, evaluate the applicable test as “○ (low possibility of powder entrainment)”, and if not, evaluate as “× (high possibility of entrainment of powder)”. And The basis for the evaluation threshold in the following formula (13) is attached to the end of this specification.

  In addition, the unit of the numerical value in FIG. 9 is mm.

≪Test: Individual test conditions and test results≫
Next, individual test conditions and test results of each test are shown in Table 1 below. In Table 1 below, the column title “W mm” is the size of the water tank and means the mold width in the actual machine (however, it is considered at the upper end of the mold). The column title “D mm” is also the size of the water tank, and means the mold thickness in the actual machine (however, it is conceived at the upper end of the mold). The column title “Air NL / min” means the gas flow rate of Ar gas introduced into the immersion nozzle during the test. This Ar gas is blown from the vicinity of the upper end of the immersion nozzle shown in FIG. And when the result of the first and second evaluation tests is “XX”, the corresponding test is evaluated as “◯ (good)”, otherwise it is evaluated as “× (defect)”. And In all tests, the opening and closing direction of the slide valve was the mold width direction.

  In addition, Test No. According to Table 1, the shape of the immersion nozzle employed in 40 is θ2 of 90 °. When such a right-angled part exists, the filling rate of the refractory deteriorates, and the possibility of the refractory being lost during use increases, so that it is difficult to adopt it in an actual machine.

(Summary)
As described above, in the first embodiment, the immersion nozzle 1 is configured as follows. That is, a pair of opposed molten steel discharge holes 2 are drilled in the peripheral wall of the immersion nozzle 1 at a position away from the inner bottom surface 3 of the immersion nozzle 1 by a predetermined distance. The inner bottom surface 3 of the immersion nozzle 1 is provided with a first rectifying protrusion 4 that extends parallel to the drilling direction of the molten steel discharge hole 2. The first rectifying protrusion 4 is narrowed at the center in the extending direction. A second rectifying protrusion that extends in parallel with the first rectifying protrusion 4 and faces the inner peripheral surface 7 of the immersing nozzle 1 across the first rectifying protrusion 4 in the bottom view of the immersion nozzle 1. 8 is provided as a pair. Each of the second rectifying protrusions 8 is formed below the first rectifying surface 13 so as to form a pair with the first rectifying surface 13 that is inclined downward toward the axial center side of the immersion nozzle 1. And a second rectifying surface 14 that is inclined upward toward the axial center side of the immersion nozzle 1. The inner diameter of the immersion nozzle 1 is Dsn, the distance between the lower end 12b of the inner peripheral opening edge 12 of the molten steel discharge hole 2 and the inner bottom surface 3 is H, and the first in the bottom view of the immersion nozzle 1 is the first. The width of the upper surface 4a of the rectifying protrusion 4 is a width at the end of the first rectifying protrusion 4 in the extending direction, and the upper surface 4a of the first rectifying protrusion 4 in the bottom view of the immersion nozzle 1. The width of the first rectifying protrusion 4 in the center in the extending direction is b, the protruding height of the first rectifying protrusion 4 is h, the second rectifying protrusion 8 and the inner bottom surface 3 and e, the height of the second straightening projection 8 in the axial direction of the immersion nozzle 1 is f, and the thickness of the second straightening projection 8 in the radial direction of the immersion nozzle 1 G, and the inclination angle of the first rectifying surface 13 with respect to the axis of the immersion nozzle 1 is θ1, When the inclination angle of the second rectifying surface 14 with respect to the axis of the immersion nozzle 1 and .theta.2, satisfies the following formulas (1) to (8).

  According to Table 1, with the above configuration, a reduction in drift in the mold width direction and a reduction in drift in the mold thickness direction are simultaneously realized at a high level.

  The first rectifying protrusion 4 may be constricted in a step shape only at the center in the extending direction instead of being smoothly narrowed in a V shape toward the center in the extending direction. In this case, the feature of the constricted portion is sharp.

<Basis for threshold of first evaluation test: FIGS. 10 to 13>

(Definition of solidification delay)
The degree of solidification delay is an indicator of the degree of solidification delay. Please refer to FIG. FIG. 10 is a first explanatory diagram (definition of coagulation delay degree) showing the basis of the evaluation threshold value of the drift degree. This degree of solidification delay Cg [%] can be thought of at each corner of the slab based on a negative segregation line visible on the cut surface obtained by cutting the slab perpendicularly to the casting direction. %] Is obtained based on the following formula (14). In the following formula (14), A [mm] is the distance between the negative segregation line and the wide surface at a point 5 [cm] away from the narrow surface, and B [mm] is the negative segregation line closest to the wide surface. The distance between the negative segregation line and the wide surface at the point. In this specification, “solidification delay degree Cg [%]” means, in principle, the largest of the four solidification delay degrees Cg [%] that can be considered from one cut surface.

(Breakout results)
Next, please refer to FIG. FIG. 11 is a second explanatory diagram (result of breakout) showing the basis of the evaluation threshold value of the drift degree. That is, continuous casting is performed for 100 charges (various casting conditions are not completely unified). For each charge, (1) one primary cutting slab is arbitrarily selected. When there is a trace of molten metal leakage on the slab surface of the next cut slab, the slab is cut perpendicularly to the casting direction so as to include the trace, and the solidification delay Cg [ (2) If there is no trace of molten metal leak on the slab surface of the primary cutting slab, the slab is cut perpendicularly to the casting direction at an arbitrarily selected location. The degree of solidification delay Cg [%] was measured on the cut surface obtained by the above. The solidification delay degree Cg [%] distribution of (1) is indicated by a solid line in the figure, and the solidification delay degree Cg [%] distribution of (2) is indicated by a broken line in the figure. According to this figure, if the solidification delay degree Cg [%] is operated so as to be less than 40, B. O. It can be seen that the occurrence of this can be prevented.

(Correspondence between drift and solidification delay)
Reference is now made to FIG. FIG. 12 is a third explanatory diagram (correspondence relationship between the degree of drift and the degree of solidification delay) showing the basis of the evaluation threshold for the degree of drift. That is, an immersion nozzle having a certain shape was made of acrylic, and the above-described drift degree TW [m / s] of the immersion nozzle was determined by a water model test. Next, an immersion nozzle having the same shape as that of the immersion nozzle was made of a refractory, and the produced immersion nozzle was operated for approximately 100 charges in an actual machine test. The casting conditions at that time were mold width D [mm]: 800 to 2100, mold thickness D [mm]: 230 to 280, and casting speed Vc [m / min]: 1.0 to 2.2. And the slab corresponding to each charge was cut | disconnected at the point of 25 m from the bottom side, and said solidification delay degree Cg [%] was measured, respectively. As a result, the drift current TW [m / s] of the immersion nozzle having a certain shape and 100 samples of the solidification delay Cg [%] corresponding to this immersion nozzle were obtained. The above test was similarly performed using four immersion nozzles having different shapes. Then, as shown in FIG. 12, the horizontal axis represents the drifting degree TW [m / s] of the immersion nozzle, and the vertical axis represents a value obtained by adding 3σ to the average value of the solidification delay degree Cg [%]. . According to this figure, in order to make solidification delay degree Cg [%] less than 40, it turns out that the drift degree TW [m / s] in a water model test needs to be 0.35 or less.

<Basis for threshold value of second evaluation test>
For example, as described in Japanese Patent Application Laid-Open No. 2003-80353, when the meniscus flow rate exceeds 0.6 m / s, there is a high possibility that powder entrainment occurs.

The perspective view of the immersion nozzle which concerns on one Embodiment of this invention Partially cutaway perspective view of an immersion nozzle according to an embodiment of the present invention Front partial sectional view of an immersion nozzle according to an embodiment of the present invention Side surface fragmentary sectional view of the immersion nozzle which concerns on one Embodiment of this invention. 4 is a sectional view taken along line VV in FIG. Image depicting the flow of molten steel when a conventional immersion nozzle is used The figure which imaged the flow of the molten steel at the time of using the immersion nozzle which concerns on one Embodiment of this invention 1st explanatory drawing regarding the test conditions of the technical effect confirmation test of the immersion nozzle which concerns on one Embodiment of this invention 2nd explanatory drawing regarding the test condition of the technical effect confirmation test of the immersion nozzle which concerns on one Embodiment of this invention. First explanatory diagram showing the basis for the evaluation threshold of the degree of drift (definition of coagulation delay) Second explanatory diagram showing the basis of the evaluation threshold of the drift degree (breakout results) Third explanatory diagram showing the basis of the evaluation threshold for the degree of drift (correspondence between drift degree and coagulation delay)

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Immersion nozzle 2 Molten steel discharge hole 3 Inner bottom face 4 of molten steel discharge hole 1st rectification protrusion 8 Second rectification protrusion

Claims (1)

In a bottomed cylindrical immersion nozzle provided for pouring molten steel held in a tundish into a mold,
On the peripheral wall of the immersion nozzle, a pair of opposed molten steel discharge holes are perforated at a position away from the inner bottom surface of the immersion nozzle by a predetermined distance,
The inner bottom surface of the immersion nozzle is provided with a first rectifying protrusion that extends in parallel to the drilling direction of the molten steel discharge hole,
The first rectifying protrusion is narrowed in the center in the extending direction,
A pair of second rectifying protrusions are provided on the inner peripheral surface of the immersion nozzle so as to extend in parallel with the first rectifying protrusion and face each other with the first rectifying protrusion sandwiched in the bottom view of the immersion nozzle. ,
Each of the second rectifying protrusions is disposed below the first rectifying surface so as to form a pair with the first rectifying surface that is inclined downward toward the axial center side of the immersion nozzle. A second rectifying surface that is inclined upward toward the axial center side of the immersion nozzle,
The inner diameter of the immersion nozzle is set to Dsn, the distance between the lower end of the inner peripheral opening edge of the molten steel discharge hole and the inner bottom surface is set to H, and the top surface of the first rectifying protrusion is viewed from the bottom of the immersion nozzle. A width at the end of the first rectifying protrusion in the extending direction, and a width of the upper surface of the first rectifying protrusion in the bottom view of the immersion nozzle, the first rectifying protrusion The width in the center of the extending direction is b, the protruding height of the first rectifying protrusion is h, the distance between the second rectifying protrusion and the inner bottom surface is e, and the axis of the immersion nozzle The height of the second rectifying protrusion in the direction is f, the thickness of the second rectifying protrusion in the radial direction of the immersion nozzle is g, and the inclination angle of the first rectifying surface with respect to the axis of the immersion nozzle is θ1 is set, and the inclination angle of the second rectifying surface with respect to the axis of the immersion nozzle is θ2. Then, the following formulas (1) to (8) are satisfied.
Immersion nozzle

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