JP4200793B2 - Immersion nozzle for continuous casting - Google Patents

Description

【００６０】
【発明の効果】
以上説明したように、本発明は、スライディングゲートの下流側に、多孔型の旋回流ノズルを配置する際に、各吐出孔から吐出される溶鋼量が強制的により均等に分配されるので、鋳型内に不均等な流動が生じにくく、鋳型内流動の左右不均等に起因する欠陥の発生を抑制し、鋳片品質を向上する効果が期待できる。
【００６１】
本発明の多孔型の旋回流ノズル及びこれを用いる連続鋳造方法は、特にスラブ連鋳に好適であり、表面疵や内部欠陥の少ないスラブ鋳片を製造することができる。
【図面の簡単な説明】
【図１】本発明の旋回流ノズルの一例をスライディングゲート越しに上方から俯瞰した図である。
【図２】本発明の旋回流ノズルの一例について、ノズル内流路を斜め上方から俯瞰した透視図である。
【図３】本発明の旋回流ノズルに内蔵される捩り板型旋回羽根の一例の正面図および平面図である。
【図４】本発明の旋回流ノズルの一例を模式的に示す縦断面図である。
【図５】下端を斜めに切り欠いた捩り板型旋回羽根の正面図である。
【図６】分散用部材を装着した旋回流ノズルの一例について、ノズル内流路を斜め上方から俯瞰した透視図である。
【図７】分流板を設けた旋回羽根の一例を示す正面図である。
【図８】スライディングゲートの開口状況を説明する上方俯瞰図である。
【図９】スライディングゲートによる偏流と旋回羽根の位置関係を説明する模式的縦断面図である。
【図１０】ノズル内流路を斜め上方から俯瞰した透視図である。
【図１１】スライディングゲートの開口部を上方から俯瞰した図である。
【図１２】吐出孔が２孔の場合の溶鋼流動状態の模式図である。図１２（ａ）は左右の吐出量が均等の状態を示し、図１２（ｂ）は左右の吐出量が不均等の状態を示す。
【符号の説明】
１…スライディングゲート
２…開口部
３…浸漬ノズル（旋回流ノズル）
４…捩り板型旋回羽根
５…上端部の稜線
６…下端部の稜線
７…旋回羽根の入口部
８…旋回羽根の出口部
９…吐出孔
１０…鋳型
１１…メニスカス
１２…モールドパウダー
１３…凝固シェル
１４…溶鋼分散用部材
１５…分流板
１６…下降流
１７…反転流[0001]
BACKGROUND OF THE INVENTION
The present invention is an immersion nozzle for continuous casting having a plurality of discharge holes, which is used in a continuous casting method of steel and which has a twisted plate type swirl blade inside to impart swirl flow to molten steel flowing down the nozzle ( Hereinafter, it is also referred to as “swirl nozzle”.
[0002]
[Prior art]
When discharging molten steel from a continuous casting immersion nozzle having a plurality of discharge holes, if the discharge amount from each discharge hole becomes uneven (single flow), the molten steel flow velocity in the mold is significantly changed. Due to the stagnation, the solidified shell cleaning action of the molten steel flow is reduced, and non-metallic inclusions and bubbles are easily trapped by the solidified shell, or the excessive molten steel flow velocity in the mold generates vortices and slabs mold powder, etc. It may cause entanglement.
[0003]
When a swirl flow is applied to the molten steel flowing down the immersion nozzle, in the case of a two-hole nozzle having two discharge holes facing the side surface of the lower end, the molten steel is forcibly distributed to the two discharge holes by centrifugal force. Therefore, fluctuations in the discharge flow rate and discharge speed from each discharge hole become small, the state of the discharge flow becomes stable, and uneven flow (single flow) hardly occurs in the mold.
[0004]
In Patent Document 1, the twist pitch Pc of the swirl blade is 0.8 to 3.0, the twist angle θ is 60 to 180 °, the outer diameter (= 2R) is 50 to 250 mm, and the thickness of the swirl blade is the outer diameter. The swirl flow nozzle is provided with a torsional plate swirl vane of 5 to 30%. The swirl flow nozzle disclosed in Patent Document 1 is an effective and practical technique in terms of the simplicity of the structure, the stabilization of the discharge flow, the strength of the swirl flow, the difficulty of blocking, and the like.
[0005]
In Patent Document 1, when a sliding gate is provided as a flow adjustment mechanism at the bottom of the tundish, the ridge line direction of the upper end portion of the torsion plate-type swirling blade is installed in parallel with the sliding direction of the sliding gate, thereby It is described that the molten steel can be evenly distributed on both sides, and a more uniform swirl flow is formed. However, when the swirl flow nozzle arranged downstream of the sliding gate has a plurality of discharge holes, each discharge nozzle is arranged even if the ridge line direction of the upper end of the torsion plate swirl blade is installed parallel to the sliding direction of the sliding gate. The discharge amount from the holes may not be sufficiently uniform, and further improvement is desired.
[Patent Document 1]
Japanese Patent Laid-Open No. 2002-239690
[Problems to be solved by the invention]
In the present invention, when a sliding gate is installed on the upstream side of a swirling flow nozzle having a plurality of discharge holes, the uniformity of the discharge amount from each discharge hole is further improved, and the flow balance in the mold (balance of meniscus flow velocity) is improved. ) To improve.
[0007]
[Means for Solving the Problems]
The present inventors have examined the discharge state of molten steel from each discharge hole when a swirl flow nozzle having a plurality of discharge holes is arranged on the downstream side of the sliding gate, by repeatedly conducting experiments and analysis by numerical calculation. .
[0008]
As a result, when the ridge line direction of the upper end of the swirl flow nozzle is aligned parallel to the sliding direction of the sliding gate, the inflow amounts to the two flow paths divided by the swirl vanes are roughly equal. However, it has been found that the molten steel tends to flow in the flow path on the side opposite to the swirl side rather than the swirl side of the swirl vane, which is not accurate, and the discharge amount from the plurality of discharge holes tends to be uneven.
[0009]
Therefore, the present inventors have further studied, and in the continuous casting apparatus provided with the swirl flow nozzle on the downstream side of the sliding gate, the molten steel is divided into each flow path divided by swirl blades built in the swirl flow nozzle. A new means that can equalize the inflow was found. The present invention provides the following swirl flow nozzles that have been proposed based on the above findings.
[0011]
Further, the first continuous casting immersion nozzle according to the present invention is disposed on the downstream side of the sliding gate, which is a flow rate adjusting mechanism of the molten steel provided at the bottom of the continuous casting tundish. An immersion nozzle having a plurality of discharge holes installed,
The ridge line direction at the upper end of the torsion plate type swirl vane is arranged at an angle in the range of 5 to 15 ° opposite to the torsion swirl direction of the torsion plate type swirl blade with respect to the sliding direction of the sliding gate. It is characterized by.
[0012]
The second continuous casting immersion nozzle according to the present invention is disposed on the downstream side of the sliding gate, which is a flow rate adjusting mechanism of molten steel provided at the bottom of the continuous casting tundish, and a twist plate type swirl blade is installed therein. An immersion nozzle having a plurality of discharge holes,
The angle formed by the horizontal direction of the plane passing through the ridge line at the lower end of the twisted plate type swirl blade is within a range of 20 to 45 °,
The torsion angle θ ′ with respect to the average value of the length in the axial direction and the length of the shortest portion of the torsion plate type swirl blade is 60 to 180 °.
[0013]
The third continuous casting immersion nozzle according to the present invention is disposed on the downstream side of the sliding gate, which is a flow rate adjusting mechanism of the molten steel provided at the bottom of the continuous casting tundish, and has a twisted plate-type swirl blade installed therein. An immersion nozzle having a plurality of discharge holes,
Disposed between the sliding gate and the twisted-plate swirl blade is a molten steel dispersion member having a polygonal or circular bar shape so that its ridgeline is parallel to the sliding direction of the sliding gate. It is characterized by that.
[0014]
The fourth continuous casting immersion nozzle according to the present invention is disposed on the downstream side of the sliding gate, which is a flow rate adjusting mechanism of the molten steel provided at the bottom of the continuous casting tundish, and has a twisted plate type swirl blade installed therein. An immersion nozzle having a plurality of discharge holes,
A diverter plate having the upper end extended in a flat plate shape or a wedge shape is arranged at the upper end of the twisted plate type swirl vane so that the ridgeline of the diverter plate is parallel to the sliding direction of the sliding gate.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
The present inventors have examined the discharge state of molten steel from each discharge hole when a swirl flow nozzle having a plurality of discharge holes is arranged on the downstream side of the sliding gate, by repeatedly conducting experiments and analysis by numerical calculation. As a result, the following phenomenon was found as a cause of the uneven discharge amount from each discharge hole.
[0017]
That is, when the sliding gate and the swirling flow nozzle are used in combination, as shown in FIGS. 8 and 9, since the opening 2 of the sliding gate 1 exists in the vicinity of the nozzle inner wall 3a, it flows into the nozzle from the sliding gate. As shown in FIG. 9, the molten steel flows down mainly in the vicinity of the inner wall 3a of the portion corresponding to the sliding gate opening 2 in the flow path of the nozzle cross section. FIG. 8 is an overhead view for explaining the opening state of the sliding gate, and FIG. 9 is a schematic longitudinal sectional view for explaining the positional relationship between the drift due to the sliding gate and the swirl blade.
[0018]
In this case, if the direction of the ridge line 5 at the upper end of the torsion plate type swirl blade 4 is set parallel to the sliding direction of the sliding gate 1 as shown in FIG. Among the flow paths A and B, in the flow path A, the flow hits the torsion plate at the inlet portion 7 of the swirl blade, whereas in the flow path B, the flow hits in the vicinity of the outlet portion 8 of the swirl blade. In Patent Document 1, the torsion angle of the swirl blade is set to 60 to 180 °. As is apparent from FIG. 11, the twisted angle of the swirl vane and the vicinity of the outlet 8 of the torsion plate and the molten steel flowing into the flow path B The effective collision area is small, and the flow path B is easier for the molten steel to flow than the flow path A. Therefore, the molten steel is not evenly distributed to the flow path A and the flow path B at the inlet of the swirl vane 4, and more molten steel flows into the flow path B side. FIG. 10 is a perspective view of the flow path in the nozzle as viewed from obliquely above, and FIG. 11 is a view of the opening of the sliding gate as viewed from above. 10 is a projected image of the opening, and a virtual line 5 ′ added for convenience to the sliding gate surface is a projected image of the ridge line 5. In FIG.
[0019]
In the downstream of the swirl vane 4, a double spiral flow is formed by the flow from the flow paths A and B. In the above case, the spiral flow is decentered to reflect that the inflow amount differs depending on the flow path. However, the discharge amount from each discharge hole 9a, 9b of the swirl flow nozzle becomes uneven. As a result, the flow in the mold becomes non-uniform, and the flow rate of the molten metal surface (meniscus) in the mold may become unstable.
[0020]
The stability of the meniscus flow rate is important for improving the quality of the slab, and it is desired that the entire meniscus has an appropriate and uniform flow rate. The meniscus flow rate is important for improving the quality of the slab, and the flow rate is preferably 20 cm / sec or more and 60 cm / sec or less. If the flow rate is slower than 20 cm / sec, the solidified shell cleaning action of the molten steel flow is impaired, encouraging trapping of bubbles and non-metallic inclusions in the solidified shell, and if the flow rate is more than 60 cm / sec, This is because vortexes are generated on the surface of the molten metal and the mold powder is entrained, both of which cause deterioration of cast slab quality such as an increase in inclusion defects.
[0021]
Further, as an indicator of the uniformity of the meniscus flow velocity, the ratio of the difference between the maximum value and the minimum value of the meniscus flow velocity distribution measured with the direction toward the center of the mold as positive is defined as the meniscus flow velocity ratio as the meniscus flow velocity ratio. When the meniscus flow rate ratio is 0.8 or less, particularly 0.4 or less, it is possible to obtain a slab of good quality as a whole.
[0022]
As an example, FIGS. 12 (a) and 12 (b) show schematic views of a molten steel flow state in a continuous casting machine using a rectangular mold when there are two discharge holes. The discharge flow collides with the short side of the mold, and a part thereof becomes the downward flow 16 as it is, but the other part becomes the reverse flow 17 in the direction of the meniscus 11 and rises along the short side of the mold, and then the mold near the meniscus. A horizontal flow toward the center is formed.
[0023]
As shown in FIG. 12A, when the molten steel is uniformly discharged from the left and right discharge holes 9 of the nozzle 3, the reverse flow from the mold short side 10a and the center of the mold in the vicinity of the meniscus 11 are directed. The flow is also uniform and stable, and a slab of good quality can be obtained.
[0024]
On the other hand, as shown in FIG. 12B, when the molten steel is discharged unevenly from the left and right discharge holes 9 of the nozzle 3, the strongly discharged side (the arrow indicating the flow is thick). In this case, the discharge flow, the reversal flow, and the flow toward the mold center in the vicinity of the meniscus have large values, and entrainment of the mold powder 12 or the like occurs. In addition, on the weakly ejected side (the side where the flow arrow is thin), the reverse flow is also weak, the flow toward the mold center in the vicinity of the meniscus 11 is also stagnated, and bubbles and non-metal in the solidified shell 13 are stagnant. Helps capture inclusions. Therefore, on either side, deterioration of slab quality occurs. Here, the vicinity of the meniscus means from the meniscus surface to a depth of about 100 mm.
[0025]
As a method for measuring the meniscus flow velocity, a Karman vortex velocimeter or the like can be used, but the meniscus flow velocity ratio is calculated from the measured value with a propeller velocimeter by a water model experiment under the same conditions or the calculated value by numerical analysis. Alternatively, the measurement can be performed for 30 seconds at several meniscus locations, and the average value can be used as the meniscus flow velocity at each location to obtain the flow velocity distribution in the meniscus, and the meniscus flow velocity ratio can be calculated.
[0026]
The present inventors have found that the discharge amount from the plurality of discharge holes of the swirl flow nozzle becomes uneven as a result of reflecting the phenomenon described above. Therefore, the present inventors have further studied, and in the continuous casting apparatus provided with the swirl flow nozzle on the downstream side of the sliding gate, the molten steel is divided into each flow path divided by swirl blades built in the swirl flow nozzle. A new means that can equalize the inflow was found. The present invention provides the following swirl flow nozzles that have been proposed based on the above findings.
[0027]
FIG. 1 is a view of an example of a first swirl flow nozzle provided by the present invention as seen from above through a sliding gate. FIG. 2 is a perspective view of an example of the first swirl flow nozzle as seen from above the nozzle flow path obliquely from above.
[0028]
As shown in FIGS. 1 and 2, the first swirl flow nozzle provided by the present invention is disposed on the downstream side of a sliding gate 1 which is a flow rate adjusting mechanism for molten steel provided at the bottom of a tundish for continuous casting. An immersion nozzle having a plurality of discharge holes, in which a torsion plate-type swirl vane is installed, and the ridge line direction 5 at the upper end of the torsion plate-type swirl vane is located inside the immersion nozzle. It is arranged with a shift angle a in the range of 5 to 15 ° in the direction opposite to the torsional turning direction of the torsion plate type swirl blade with respect to the moving direction. 2 is a projection image of the opening, and a virtual line 5 ′ added for convenience to the sliding gate surface is a projection image of the ridge line 5. In FIG.
[0029]
When the ridge line direction of the upper end of the swirl flow nozzle is aligned parallel to the sliding direction of the sliding gate, the amount of inflow into the two flow paths divided by the swirl vane is roughly equal. In order to reflect the above-described phenomenon, it is not accurate, and the discharge amount from the plurality of discharge holes tends to be uneven.
[0030]
On the other hand, the swirling flow nozzle of the present invention reduces the sliding gate opening area facing the counter-swirl side by installing the ridge line direction of the upper end of the swirl blade by shifting it from parallel to the counter-swirl direction by several degrees, Since the area facing the swirl side can be enlarged, the amount of inflow into the two flow paths on both sides of the swirl vane is equalized. As a result, the discharge amount from the plurality of discharge holes existing on the downstream side of the swirl vane is equalized, and as a result, the non-uniformity of molten steel flow (non-uniform meniscus flow velocity distribution) is corrected, the stability of operation and the slab A quality improvement effect can be obtained. The shift angle has some fluctuations in the optimum value depending on the molten steel flow rate and swirl blade twist angle, and it is desirable to check and adjust the discharge flow rate by water model experiment etc., but according to the experiments by the present inventors, When the shifting angle is in the range of 5 ° to 15 °, a clear improvement effect was observed on the whole.
[0031]
FIG. 3A is a front view of an example of a torsion plate type swirl blade 4 incorporated in the first swirl flow nozzle, and FIG. 3B is a plan view. However, the torsion angle θ of the blades in FIGS. 3A and 3B is different. FIG. 4 is a cross-sectional view schematically showing an example of the swirl flow nozzle 3 of the present invention. In FIG. 4, a torsion plate having an outer diameter equal to the inner diameter of the nozzle so that the two-layer sliding gate 1 ′ composed of the two slide members 1a and 1b is fitted to the nozzle flow path without any gap. A mold swirl vane 4 is arranged. The shape of the swirl vane used for each swirl flow nozzle including the first swirl flow nozzle is as follows. The outer diameter D is 50 to 250 mm, the torsion length L is 30 to 200% of the outer diameter, and the vane thickness T is The outer diameter is preferably 5 to 30%, and the twist angle θ is preferably 60 to 180 °.
[0032]
Here, the reason why it is preferable to define the dimensions of the swirl vanes as described above is as follows.
[0033]
(1) Outer diameter of blades When the outer diameter of the swirl vane is less than 50 mm, the swirl vane provides a predetermined swirl flow so that the molten steel flow path is too narrow and the immersion nozzle is likely to be blocked. Sex worsens. On the other hand, when the outer diameter exceeds 250 mm, the immersion nozzle body becomes enormous and handling becomes difficult.
[0034]
(2) The length of the torsion part of the blade If a necessary twist angle is given at less than 30% of the outer diameter of the blade, a steep rotation will be given, the flow resistance will increase, and the required molten steel flow velocity will not be obtained. Reduce productivity. On the other hand, if it exceeds 200% of the outer diameter of the blade, the rotational pitch of the blade torsion is too slow, and a sufficient swirling speed cannot be given to the swirling flow.
[0035]
(3) Blade Thickness If the thickness of the outer diameter of the blade is less than 5%, the strength of the structure is insufficient and there is a risk of breakage during casting. On the other hand, when it exceeds 30% of the outer diameter of the blade, the thickness is unnecessary in strength, and the flow resistance is increased unnecessarily, and the immersion nozzle is likely to be blocked.
[0036]
(4) Torsion angle θ of the blade
When the twist angle θ is less than 60 °, the area occupied by the swirling blades in the cross-section of the flow path in the submerged nozzle is reduced, and a uniform swirling flow cannot be obtained. On the other hand, even if the twist angle exceeds 180 °, the effect is not particularly enhanced, the flow resistance is increased, and the immersion nozzle is easily blocked.
[0037]
FIG. 5 is a front view of an example of a twisted plate type swirl blade used in the second swirl flow nozzle. The second swirl flow nozzle provided by the present invention is a swirl flow nozzle that is disposed on the downstream side of the sliding gate 1 and has a twist plate swirl blade installed therein, and has a plurality of discharge holes. The plate-type swirl blade 4 ′ has a horizontal ridgeline 5 at its upper end, and an angle between the plane passing through the ridgeline 6 at its lower end and the horizontal direction is in the range of 20 to 45 °, and is the length of the longest axial portion. The twist angle θ ′ with respect to the average value of the lengths of the shortest portions is 60 to 180 °.
[0038]
By extending the lower end of the twisted-plate swirl vane into a shape having an angle with respect to the horizontal plane, swirl flow formation can be promoted, and as a result, the flow of discharged molten steel can be made uniform. This reduces the difference between the distance that the molten steel to the flow path A collides with the swirl vane and flows down along the blade and the distance that the molten steel to the flow path B flows down along the blade against the drift due to the sliding gate. This is because it is possible to obtain a uniform swirling flow having the same strength as the swirling flow by the flow path A and the flow path B. The length ΔL extending the lower end is preferably 30 to 50% of the swirl vane length.
[0039]
Similar to the first swirl flow nozzle and swirl vane, the twisted plate type swirl blade used for the second swirl flow nozzle is twisted swirl of the swirl blade with the ridge line direction at the upper end of the sliding gate sliding direction. It is preferable to arrange with an angle in the range of 5 to 15 ° opposite to the direction. In that case, the ridge line 5 at the upper end is horizontal, and the ridge line 4 at the lower end is a corner on the opposite side from the corner point P1 at the diagonal position with respect to the corner point P1 near the sliding gate opening of the upper end ridge line. It is particularly preferable to make an upward angle with respect to the horizontal direction toward the point Q2.
[0040]
FIG. 6 is a perspective view of an example of the third swirling flow nozzle as seen from above the flow path in the nozzle obliquely from above. The third swirl flow nozzle provided by the present invention is a swirl flow nozzle that is disposed on the downstream side of the sliding gate 1 and has a plurality of discharge holes in which a twist plate swirl blade is installed. 1 and the torsion plate-type swirl vane 4 are arranged such that a dispersion member 14 made of molten steel having a polygonal or circular bar shape in cross section is parallel to the sliding direction of the sliding gate. It is a thing. In FIG. 6, a virtual line 5 ′ provided for convenience on the sliding gate surface is a projected image of the ridge line 5.
[0041]
By installing a member that disperses the drift due to the sliding gate between the sliding gate and the swirl vane, it is possible to make the distribution of molten steel flowing into the swirl vane more uniform, resulting in a uniform flow of discharged molten steel. It can be performed. The shape of the dispersing member may be a rod having a diameter of 10 mm or more and a length equal to the inner diameter of the nozzle, and a polygonal or circular (including ellipse) cross section. The installation position is 50% of the inner diameter of the nozzle. To 200% is desirable. Normally, only one dispersing member is provided at the center in the width direction of the sliding gate (horizontal direction perpendicular to the sliding direction), but two or more members may be arranged horizontally.
[0042]
FIG. 7 is a front view of an example of a torsion plate type swirl blade used in the fourth swirl flow nozzle. A fourth swirl flow nozzle provided by the present invention is a swirl flow nozzle that is disposed on the downstream side of the sliding gate 1 and has a plurality of discharge holes in which a twist plate swirl blade is installed. A diverting plate 15 for diverting molten steel, in which the upper end of the swirl vane 4 is extended in a flat plate shape or a wedge shape in parallel with the longitudinal direction of the swirl vane, and the ridge line of the diverting plate is parallel to the sliding direction of the sliding gate. It is arranged to become. In FIG. 7, a virtual line drawn for convenience around the swirl vane indicates a flow path in the nozzle.
[0043]
The upper end of the swirl vane is extended into a flat plate or wedge shape to form a flow dividing plate, and the molten steel from the sliding gate is divided on the upstream side of the swirl vane to equalize the amount of molten steel flowing into each flow path of the swirl vane. As a result, the flow of discharged molten steel can be made uniform. The height of the flow dividing plate is 50% to 150% of the swirl blade length
Is desirable. The width of the flow dividing plate is preferably the same as the length of the upper end of the swirl vane.
[0047]
By combining two or more means employed in the swirl flow nozzle, it becomes possible to make the discharge amount from the plurality of discharge holes of the swirl flow nozzle more uniform. For example, in the first invention, it is possible to use swirl vanes in which the upper and lower ends of the second invention are cut obliquely, or the molten steel dispersing member of the third invention.
[0048]
【Example】
Hereinafter, description will be made based on the results of experiments conducted to confirm the effects of the present invention.
[0049]
A continuous casting experiment of a low-carbon steel slab (thickness 250 mm, width 1600 mm) was performed at a casting speed of 1.8 m / min, and the meniscus flow rate and cleanliness index were evaluated. Test conditions and results are shown in Table 1.
[0050]
The meniscus flow rate ratio, which is an index of the meniscus flow rate, represents the difference between the maximum value and the minimum value of the meniscus flow rate in the numerical analysis result as a ratio to the average meniscus flow rate.
[0051]
The cleanness index, which is an index of the quality of the slab, is a size included in a 10 mm square at a position 400 mm in the width direction from the width end face of a slab that has been continuously cast under the same conditions as the numerical analysis. The number of inclusions having a thickness of 50 μm or more was measured with an optical microscope at a pitch of 10 mm in the thickness direction and evaluated.
[0052]
Examples 1, 2 and 3 use nozzles in which swirl vanes are installed with -8 °, -5 ° and -15 ° shifted from the swivel direction starting from the sliding direction of the sliding gate, respectively. . A minus angle means the direction opposite to the torsional turning direction. The meniscus flow rate ratio in Example 1 was the best, and good results were also obtained in Examples 2 and 3.
[0053]
In Example 4, a nozzle in which a round bar having a diameter of 15 mm was arranged in the nozzle diameter direction in parallel with the sliding direction was applied 10 cm downstream of the sliding gate, and good results were obtained.
[0054]
Example 5 is an example in which a wedge-shaped flow dividing plate having a length of 100 mm is arranged at the upper end of the swirl blade, and good results were obtained.
[0056]
In Example 7, the nozzle having the swirl blade having the shape shown in FIG. 5 and having the shape shown in FIG. 5 notched so that the angle formed between the lower edge side ridge line of the swirl blade and the horizontal direction is 35 °, In this example, the gates were arranged in parallel with the sliding direction of the gate, and good results were obtained.
[0057]
On the other hand, Comparative Examples 1, 2 and 3 have nozzles installed with swirling blades shifted in parallel (0 °), + 5 °, and −20 ° with respect to the swiveling direction, starting from the sliding direction of the sliding gate. It is what was used. In both cases, the meniscus flow rate ratio and the cleanliness within the allowable range were obtained, but the example of the present invention was further improved.
[0058]
The comparative example 4 is an example using the nozzle of the conventional shape which does not use a turning blade. In this case, the present invention was very inferior as well as Comparative Examples 1 to 3 using swirl vanes.
[0059]
[Table 1]

[0060]
【The invention's effect】
As described above, according to the present invention, the amount of molten steel discharged from each discharge hole is forcibly and evenly distributed when the porous swirl flow nozzle is disposed on the downstream side of the sliding gate. It is difficult to generate uneven flow in the mold, and it is possible to suppress the occurrence of defects due to left and right non-uniform flow in the mold and to improve the slab quality.
[0061]
The porous swirl nozzle of the present invention and the continuous casting method using the nozzle are particularly suitable for slab continuous casting, and can produce a slab cast with few surface defects and internal defects.
[Brief description of the drawings]
FIG. 1 is a view of an example of a swirl flow nozzle according to the present invention viewed from above through a sliding gate.
FIG. 2 is a perspective view of an example of a swirling flow nozzle according to the present invention, as seen from an oblique upper side of a flow path in the nozzle.
FIG. 3 is a front view and a plan view of an example of a twisted plate type swirl blade built in the swirl flow nozzle of the present invention.
FIG. 4 is a longitudinal sectional view schematically showing an example of a swirl flow nozzle according to the present invention.
FIG. 5 is a front view of a torsion plate type swirl blade with a lower end cut obliquely.
FIG. 6 is a perspective view of an example of a swirl flow nozzle equipped with a dispersion member, as seen from above the nozzle flow path obliquely from above.
FIG. 7 is a front view showing an example of a swirl vane provided with a flow dividing plate.
FIG. 8 is an upper overhead view for explaining the opening state of the sliding gate.
FIG. 9 is a schematic longitudinal cross-sectional view for explaining the positional relationship between drifting by a sliding gate and swirl vanes.
FIG. 10 is a perspective view of the flow path in the nozzle as viewed from obliquely above.
FIG. 11 is an overhead view of an opening of a sliding gate.
FIG. 12 is a schematic view of a molten steel flow state when there are two discharge holes. FIG. 12A shows a state where the left and right discharge amounts are equal, and FIG. 12B shows a state where the left and right discharge amounts are uneven.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Sliding gate 2 ... Opening part 3 ... Immersion nozzle (swirl flow nozzle)
DESCRIPTION OF SYMBOLS 4 ... Torsion board type swirl blade 5 ... Edge line 6 of upper end part ... Ridge line 7 of lower end part ... Entrance part 8 of swirl blade ... Outlet part 9 of swirl blade ... Discharge hole 10 ... Mold 11 ... Meniscus 12 ... Mold powder 13 ... Solidification Shell 14 ... Molten steel dispersion member 15 ... Shunt plate 16 ... Downflow 17 ... Reverse flow

Claims (5)

A submerged nozzle having a plurality of discharge holes, disposed on the downstream side of a sliding gate, which is a flow rate adjustment mechanism of molten steel provided at the bottom of a continuous casting tundish, and provided with twisted-plate-type swirl vanes inside,
The direction of the ridgeline at the upper end of the twisted-plate swirl blade is relative to the sliding direction of the sliding gate.
An immersion nozzle for continuous casting, characterized in that it is disposed at an angle in the range of 5 to 15 ° in the direction opposite to the torsional turning direction of the twisted plate type swirl vane.   The torsion plate-type swirl blade has an outer diameter of 50 to 250 mm, a torsion part length of 30 to 200% of the outer diameter, a blade thickness of 5 to 30% of the outer diameter, and a twist angle θ of 60 to 180. The continuous casting immersion nozzle according to claim 1, which has a shape of °. A submerged nozzle having a plurality of discharge holes, disposed on the downstream side of a sliding gate, which is a flow rate adjustment mechanism of molten steel provided at the bottom of a continuous casting tundish, and provided with twisted-plate-type swirl vanes inside,
The angle formed by the horizontal direction of the plane passing through the ridge line at the lower end of the twisted plate type swirl blade is within a range of 20 to 45 °,
An immersion nozzle for continuous casting, characterized in that the twist angle θ ′ with respect to the average value of the length in the axial direction and the length of the shortest portion of the torsion plate type swirl blade is 60 to 180 °. A submerged nozzle having a plurality of discharge holes, disposed on the downstream side of a sliding gate, which is a flow rate adjustment mechanism of molten steel provided at the bottom of a continuous casting tundish, and provided with twisted-plate-type swirl vanes inside,
Disposed between the sliding gate and the twisted-plate swirl blade is a molten steel dispersion member having a polygonal or circular bar shape so that its ridgeline is parallel to the sliding direction of the sliding gate. An immersion nozzle for continuous casting characterized by the above. A submerged nozzle having a plurality of discharge holes, disposed on the downstream side of a sliding gate, which is a flow rate adjustment mechanism of molten steel provided at the bottom of a continuous casting tundish, and provided with twisted-plate-type swirl vanes inside,
A flow dividing plate having the upper end extended into a flat plate shape or a wedge shape is arranged at the upper end of the twisted plate type swirl blade so that the ridge line of the flow dividing plate is parallel to the sliding direction of the sliding gate , and the flow dividing plate The continuous casting dipping is characterized in that the height is 50 to 150% of the length of the twisted plate type swirl blade, and the width of the flow dividing plate is the same as the upper end length of the twisted plate type swirl blade. nozzle.

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