WO2013161578A1 - 連続鋳造装置の浸漬ノズル - Google Patents
連続鋳造装置の浸漬ノズル Download PDFInfo
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- WO2013161578A1 WO2013161578A1 PCT/JP2013/060963 JP2013060963W WO2013161578A1 WO 2013161578 A1 WO2013161578 A1 WO 2013161578A1 JP 2013060963 W JP2013060963 W JP 2013060963W WO 2013161578 A1 WO2013161578 A1 WO 2013161578A1
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- Prior art keywords
- nozzle
- flow
- hole
- discharge hole
- immersion nozzle
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/10—Supplying or treating molten metal
- B22D11/11—Treating the molten metal
- B22D11/114—Treating the molten metal by using agitating or vibrating means
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/10—Supplying or treating molten metal
- B22D11/103—Distributing the molten metal, e.g. using runners, floats, distributors
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D41/00—Casting melt-holding vessels, e.g. ladles, tundishes, cups or the like
- B22D41/50—Pouring-nozzles
- B22D41/507—Pouring-nozzles giving a rotating motion to the issuing molten metal
Definitions
- the present invention relates to a submerged nozzle of a continuous casting apparatus, and more particularly to a continuous casting apparatus that continuously manufactures steel pieces such as slabs, blooms and billets from molten steel. It contributes to the improvement of slab quality.
- an immersion nozzle is widely used to inject molten steel from a tundish into a mold.
- the immersion nozzle has an important role in preventing molten steel from coming into direct contact with the atmosphere and being reoxidized, and is an important refractory material that greatly contributes to improving the quality of the slab.
- the flow of the molten steel discharged from the immersion nozzle into the mold affects the slab quality. For example, in a rectangular mold such as a bloom or billet, supplying a discharge flow as evenly as possible to each mold surface is important for preventing cracking of a cast piece.
- Patent Document 1 discloses that a discharge flow is swung in a tangential direction at a plurality of positions symmetrical with respect to the center of discharge and is discharged at an angle of 45 ⁇ 10 ° with respect to a rectangular mold surface. A method of obtaining a flow has been proposed. In addition, the discharge holes have been proposed to be straight or curved. Patent Document 2 proposes a nozzle in which a part of the inner wall of the discharge hole coincides with the tangent of the inner periphery of the nozzle.
- Patent Document 3 a nozzle formed by making the discharge direction of the discharge hole have an angle in the circumferential direction with respect to the radial direction from the center thereof, the reaction force when the molten steel is discharged is immersed in the nozzle.
- Patent Document 4 proposes a method in which the discharge hole is inclined with respect to the radial direction, the immersion nozzle has two upper and lower parts, and the lower nozzle rotates around the vertical axis.
- the conventional immersion nozzle for molten metal continuous casting is configured as described above.
- the conventional proposed structure has an unstable swirling flow and a low flow velocity, which is sufficient to prevent inclusions and bubbles from being trapped by the solidified shell. The effect was not obtained. Further, no further effect was obtained for casting having a circular cross section such as a round billet.
- the present invention has been made to solve the above-described problems.
- the present invention has two or more discharge hole channels on the cylindrical side surface of the immersion nozzle, and the discharge holes in a horizontal section when the immersion nozzle is used.
- An object of the present invention is to form a stable swirling flow of molten steel in the mold and contribute to the improvement of the slab quality by a straight line in which the outer side wall is refracted in the flow path.
- the immersion nozzle for continuous casting of molten metal has two or more discharge hole channels on the cylindrical side surface of the immersion nozzle having nozzle holes, and the discharge nozzle channels in the horizontal section when the immersion nozzle is used.
- the first and second inner sidewalls and the first and second outer sidewalls are formed by straight lines formed by being refracted by the inner and outer refracting points, and the discharge hole flow path of the immersion nozzle Inside, two straight lines formed by the first inner side wall and the first outer side wall and a straight line connecting the first and second intersections where the outer edge of the nozzle hole intersects, and perpendicular to the straight line, pass through the hole center of the nozzle hole.
- the first angle formed by the first center line is 45 to 135 °, the thickness of the immersion nozzle is t, and the distance from the center of the nozzle hole to the inner refractive point is a. , From the hole center to the outer refraction point When the distance is she is b, and the ri to the radius of the nozzle hole, 0.2 ⁇ (a ⁇ ri) / t and (b ⁇ ri) /t ⁇ 0.9
- the configuration is as follows.
- the immersion nozzle for continuous molten metal casting according to the present invention is configured as described above, the following effects can be obtained. That is, the cylindrical side surface of the immersion nozzle having nozzle holes has two or more discharge hole channels, and the first and second inner side walls and the first and second side walls of the discharge hole channel in a horizontal section when the immersion nozzle is used. (2) Since the outer side wall is constituted by a straight line formed by refracting at the inner and outer refracting points, it is possible to mold only by improving the shape of the discharge hole channel of the immersion nozzle without changing other equipment. A stable swirling flow of molten steel can be generated in the inside, contributing to improvement in slab quality.
- FIG. 1 It is a cross-sectional schematic diagram which shows the nozzle inner hole and discharge hole of the immersion nozzle for molten metal continuous casting by this invention. It is a cross-sectional schematic diagram which shows only the cross section of the nozzle inner hole and discharge hole of FIG. It is an expansion schematic diagram of the discharge hole of FIG. It is a schematic diagram which shows the structure in the case of a pair of discharge hole with the other form of FIG. It is a schematic diagram which shows the structure in the case of a pair of discharge hole with the other form of FIG. It is a schematic diagram which shows the structure in the case of a pair of discharge hole with the other form of FIG. It is a schematic diagram which shows the structure in the case of a pair of discharge hole with the other form of FIG. It is the model which shows the state which looked at the discharge flow velocity measurement position in the discharge hole of FIG.
- FIG. 6 is a schematic diagram showing a shape in which discharge hole channels are provided in the tangential direction of nozzle holes in the prior art (Patent Documents 1 to 4).
- FIG. 1 It is a schematic diagram which shows the shape which provided the discharge hole flow path in the tangent direction of the nozzle hole of the past (patent documents 1 and 3). It is a schematic diagram at the time of setting it as the shape which refracted only the inside of the discharge hole flow path as a comparative example. It is a schematic diagram at the time of setting it as the shape which refracted only the outside of the discharge hole channel as a comparative example. It is the schematic diagram at the time of making the bottom hole in the nozzle bottom with the other form of FIG.
- An object of the present invention is to provide an immersion nozzle for molten metal continuous casting that can generate a stable swirling flow of molten steel in a mold and contribute to the improvement of slab quality.
- the discharge flow flowing out from the immersion nozzle through the discharge hole is (1) the immersion nozzle.
- Two points are important: a certain amount of inclination with respect to the radial direction as viewed from the central axis of the nozzle, and (2) that the state of the discharge flow is stably continued. From such a viewpoint, various discharge hole shapes were devised, water model experiments were conducted to evaluate each hole shape, and the immersion nozzle according to the present invention was developed.
- the water model of the immersion nozzle is a water model assuming a ⁇ 200 mm round billet continuous casting machine.
- the process was carried out under the condition that the casting and drawing speed was 2.0 m / min.
- FIG. 11 the shape in which the discharge hole channel 2 is provided in the tangential direction of the nozzle hole 1 as in documents 1 to 4, the tangential direction of the nozzle hole 1 as in documents 1 and 3 of FIG.
- FIGS. 7 shows a state in which the measurement position is viewed from the outside of the discharge hole channel 2 of the immersion nozzle 3, and FIG. 8 shows a cross section at the position of the discharge hole channel 2.
- the measurement positions A and B are inside the discharge hole flow path where a swirl flow is to be generated, and C and D are outside.
- FIG. 9 shows the discharge flow velocity measurement result in the case of the cross section of the discharge hole channel 2 of FIG. 2 where a sufficient swirl flow was obtained.
- the horizontal axis indicates the change over time
- the vertical axis indicates the relative value of the average flow rate every 10 seconds, indicating a state where the value is high on the top and low on the bottom.
- FIG. 10 shows the discharge flow velocity measurement result in the case of the cross section of the discharge hole channel 2 of FIG. 12 where a sufficient swirl flow was not obtained. Comparing the flow velocity values on the same horizontal plane (D and B, C and A) of the discharge hole flow path 2, there is almost no difference between the flow speeds D and C outside the discharge hole flow path 2 and the flow speeds B and A inside. Occasionally, a reverse phenomenon was observed in which the flow velocity was faster on the inside (B, A) of the curve. The mold under measurement was in an unstable state in which swirling flow was repeatedly generated / disappeared.
- FIG. 3 is a schematic diagram showing the flow in the flow path when the discharge hole flow path 2 is refracted.
- the B and A sides shown in FIG. 7 are the inner sides when the flow path is refracted.
- a flow is generated on the downstream side of the first inner side wall 6 at the inner refraction point 5 without being along the tube wall.
- a vortex 6a is generated on the downstream side of the inner refraction point 5, and as a result, the flow velocity on the downstream side of the inner refraction point 5 inside the refraction part 6A is reduced.
- the flow velocity is increased outside the refracting portion 6A due to a decrease in the flow velocity inside the refracting portion 6A.
- the flow outside the refracting portion 6 ⁇ / b> A becomes a flow inclined with respect to the radial direction viewed from the center of the immersion nozzle 3 due to the downstream side wall of the outer refraction point 9.
- the two effects of the increase in the flow velocity outside the refracting portion 6 due to the generation of the vortex 6a by the inner refracting point 5 and the flow direction by the outside of the refracting portion 6A work.
- the flow inclined with respect to the radial direction seen from the center continues stably, and as a result, a stable swirling flow is produced.
- the discharge hole channel 2 is preferably installed at a rotationally symmetric position below the immersion nozzle 3. By doing so, the swirl motion can be continued by the flow from the discharge hole channel 2. Further, the number of installed discharge hole channels 2 is preferably 2 to 4, but may be more than that. In the present invention, the technically most important point is that the inner refraction point 5 has a structure in which the discharge hole channel 2 is refracted rather than curved, and the flow is separated from the wall surface to generate a stagnation portion.
- both side surfaces of the discharge hole channel 2 in the horizontal cross section when the immersion nozzle 3 is used are constituted by substantially refracted straight lines.
- a vortex 6a can be created downstream of the inner refraction point 5 and the flow velocity outside the flow path can be increased.
- the flow direction can be directed in a direction inclined with respect to the radial direction viewed from the center of the nozzle hole 1, and the swirling flow is generated. it can. By combining these, a stable swirl flow is produced.
- the walls on both sides of the flow path 2 are the same. It is important that the light is refracted in the direction and the refraction angle is within a certain range. When only the inner side is refracted as shown in FIG. 13 and the opposite side is a straight line, the flow is discharged almost radially from the nozzle hole 1 along the straight wall surface, and a swirling flow cannot be generated in the mold. Further, even when only the outer side is refracted as shown in FIG. 14, a sufficient swirling flow cannot be generated in the mold.
- the inner refraction point 5 and the outer outer refraction point 9 of the discharge hole channel 2 may be provided with a small R for convenience in manufacturing. However, particularly on the inner side, if R is too large, the refraction channel approaches the curved channel and a sufficient swirling flow cannot be obtained. Specifically, R is 5 mm or less, more preferably 3 mm or less. Further, the inner and outer R may have different curvatures.
- the second angle ⁇ formed by the two straight lines formed by the second inner side wall 7 and the second outer side wall 11 on the outer side of the immersion nozzle 3 and the second center line 16 between the extended lines is 15 to 85 °. Is more preferable, and 25 to 75 ° is more preferable.
- the angle is less than 15 °, there is no flow separating from the tube wall in the inner flow path of refraction, so that a sufficient flow rate difference cannot be obtained in the flow path, and the flow is discharged almost radially from the center of the nozzle. Therefore, the swirl flow in the mold cannot be obtained.
- the turning flow velocity decreases. This is considered to be because the growth of vortices generated on the inner surface side becomes too large, and the increase in the flow velocity on the outer side is suppressed.
- the thickness of the second outer surface side wall 11 and the nozzle outer surface 3a is reduced, problems such as crack peeling of the immersion nozzle 3 during use are likely to occur, and it is not a good idea to make it larger than this.
- the first angle ⁇ formed by the first center line 15 passing through the hole center P between the two straight lines formed by the first inner side wall 6 and the first outer side wall 10 inside the immersion nozzle 3 from the refracting portion 6A is 45 ⁇ . It is preferably 135 °. More preferably, it is 50 to 120 °. If ⁇ is less than 45 ° or greater than 135 °, the brick between the nozzle hole 1 and the discharge hole flow path 2 becomes thin, making it difficult to manufacture.
- the distance Wi between the pair of first and second intersections 13 and 14 where the nozzle hole 1 intersects two straight lines formed by the first inner side wall 6 and the first outer side wall 10 inside the immersion nozzle 3 from the refracting portion 6A is as follows.
- the radius ri of the nozzle hole is ri, it is preferably 0.15 ⁇ Wi / ri ⁇ 1.6, more preferably 0.2 ⁇ Wi / ri ⁇ 1.4. If it is less than 0.15, it is not preferable because the discharge hole channel 2 becomes too small to secure a flow rate, and if it is larger than 1.6, the thickness with the nozzle outer surface 3a becomes thin when it is refracted. This is not preferable because problems such as crack peeling of the immersion nozzle 3 during use are likely to occur.
- (a ⁇ ri) / t is 0.2 or more. Is more preferable, and 0.3 or more is more preferable.
- (a-ri) / t is less than 0.2, the flow from the nozzle hole 1 of the submerged nozzle 3 toward the discharge hole flow path 2 does not develop sufficiently, so that the downstream side from the refraction points 5 and 9 The vortex growth at this point does not occur sufficiently. Therefore, a sufficient swirl flow cannot be obtained.
- the maximum value of (a ⁇ ri) / t is not particularly defined, but is determined by the shape of the discharge hole channel 2 described later.
- (b ⁇ ri) / t is preferably 0.9 or less, more preferably 0.85 or less. It is. If the ratio is larger than 0.9, the flow outside the refracting portion cannot be sufficiently exerted by the side wall on the downstream side of the outer refracting point 9 so that the flow is inclined with respect to the radial direction viewed from the center of the nozzle hole 1. It is not preferable.
- the width of the discharge hole channel 2 is basically constant, but may not be constant. Specifically, the inner width from the outer refraction point 9 changes, and it may be larger at the entrance of the discharge hole channel 2 and smaller at the refraction part 6A side or vice versa. Similarly, the width of the outer side than the inner refraction point 5 may be changed. Furthermore, the width may change before and after the refracting portion 6A.
- a bottom hole 17 may be provided on the bottom surface of the nozzle as shown in FIG.
- the amount of molten steel passing through the immersion nozzle 3 is large, and the discharge flow from the discharge hole channel 2 provided on the side surface is large in comparison with the mold cross-sectional area. If it is too large, the discharge flow that produces the swirl flow becomes too strong, the meniscus fluctuation becomes large, and casting may become unstable. In this case, the bottom hole 17 is provided, and the flow rate required to give the swirling flow is made to flow out from the side discharge hole flow path 2, and the remaining molten steel flow is introduced from the bottom hole 17 to the downstream of the mold. It is possible to achieve both the turning state and the suppression of meniscus fluctuation.
- the open area of the bottom hole 17 and S b upon the opening area of the discharge hole channel 2 provided on the side surface, the total opening area S t to the sum of the open area of the bottom hole 17, the bottom related to the molten steel outflow S b / S t from the hole 17, if the value is large, it becomes larger proportion of amount of molten steel flowing out from the bottom hole 17 for the molten steel passing amount of the nozzle.
- S b / S t is preferably 0 to 0.4. More preferably, it is 0.1 to 0.35.
- the shape of the cross section of the bottom hole 17 in the direction parallel to the bottom hole wall 17a is basically circular, but may be a polygonal shape.
- the shape in the cross-sectional direction perpendicular to the bottom hole wall 17a can be a straight line, a curved line, a combination of a plurality of straight lines or curved lines, and a convex shape at the center.
- a plurality of bottom holes 17 can be formed.
- the S b is the sum of the areas of the bottom hole 17. It is also possible to provide a plurality of bottom holes 17 having a discharge direction that is inclined with respect to the nozzle axis, or to prevent the discharge direction from intersecting the nozzle axis.
- a round billet, a square billet or a bloom having a diameter or a long side dimension of 600 mm or less in a horizontal section is suitable, and a passing amount of molten steel is 0.3 to 2.0 ton / Min operation is suitable.
- the shape of the mold is a rectangle or a shape close to a circle, a swirling flow is generated in the entire mold.
- the long side such as a slab has a very long shape, the swirling flow develops well around the nozzle.
- a swirl flow hardly occurs around the mold short side wall far from the nozzle.
- the immersion nozzle 3 according to the present invention relates to the shape of the discharge hole channel 2 and is not restricted by the structure of the nozzle hole 1 and the nozzle material.
- a structure of the nozzle hole 1 the same effect can be obtained by a general straight pipe structure, a structure in which the diameter is partially changed in the middle of the pipe, a structure having irregularities in the inner pipe, and the like.
- the nozzle material include alumina-graphite, magnesia-graphite, spinel-graphite, zirconia-graphite, alumina, clay, spinel, and fused silica. Even if the discharge hole channel 2 has an upward or downward angle with respect to the horizontal plane, the same effect as that in the horizontal direction is exhibited.
- Example and Comparative Example Using a water model simulation facility of the same scale as the actual facility, it was evaluated whether or not the swirl flow could be stably generated when the immersion nozzle 3 shown in Table 1 was used. .
- the water model of the immersion nozzle 3 is a water model assuming a ⁇ 200 mm round billet continuous casting machine. The measurement was performed under the conditions of several pieces and the casting drawing speed of 1.5 m / min.
- the swirl flow was evaluated as follows. That is, the experiment was conducted for 3 minutes, and the case where a swirling flow was constantly generated in the mold during that time was evaluated from the viewpoint of swirling flow velocity and stability.
- the swirl flow rate was “good” when it was sufficiently large, “slightly insufficient” when swirl flow was not so large, and “not generated” when it was not generated.
- stability “good” was obtained when a swirling flow was stably obtained, “unstable” when repeated circulation was generated / disappeared, and “not generated” when it did not occur.
- the water model test was carried out using various shapes of the discharge hole channel 2, and the features thereof are as follows. When there was a refraction point in the middle of the flow path, all were R5. The test results are shown in Table 1. The characteristics of each discharge hole shape are expressed as follows. 1. Tangential line: The shape illustrated in documents 1 to 4 in the shape of FIG.
- FIG. 4 shows a cross-sectional view of Invention 1 and Table 2 shows the test results.
- a sufficient turning state could not be obtained, but when the invention product 1 was used, a good turning state could be obtained regardless of the size and shape of the mold.
- the immersion nozzle 3 prepared a plurality of shapes according to the first embodiment of the present invention, and provided a round hole at the bottom of the immersion nozzle 3.
- the mold size was a rectangle of 500 ⁇ 500 mm.
- the amount of mold fluctuation in the mold was also evaluated. The results are shown in Table 4. Although swirl flow was generated under all throughput conditions, the amount of mold surface fluctuation in the mold tended to increase under high throughput conditions.
- the immersion nozzle of the continuous casting apparatus generates a stable swirling flow of molten steel in the mold only by improving the shape of the discharge hole of the immersion nozzle without changing other equipment, thereby improving the quality of the slab. Can contribute.
Abstract
Description
また、浸漬ノズルからモールド内に吐出した溶鋼の流動は鋳片品質に影響する。例えば、ブルーム、ビレット等の矩形のモールドにおいては、各モールド面に出来るだけ均等に吐出流を供給することが鋳片割れを防止するうえで重要である。一方、溶鋼をモールド内で旋回・攪拌させることで介在物や気泡が凝固シェルに捕捉されにくくなるため鋳片の表面品質も向上する。
前記モールド内で溶鋼を攪拌するために、例えばモールド近傍に電磁撹拌装置を設置し、電磁力を利用して溶鋼を撹拌させる方法が知られている。しかし、この電磁撹拌装置は極めて高価であるため、これに代わる安価なシステムで撹拌することが求められてきた。
その方法として、浸漬ノズルからの吐出流によってモールド内で旋回流を作り、これによって溶鋼を攪拌する試みがなされてきた。
また、特許文献2には、吐出孔の内壁の一部がノズル内周の接線と一致するノズルが提案されている。
また、特許文献3には、吐出孔の吐出方向をその中心からの放射方向に対して周方向に角度を持たせて形成したノズルを利用し、溶鋼が吐出するときの反作用の力を浸漬ノズルが受けるようにして、浸漬ノズル自体を鉛直軸に回転させることによって溶鋼流を旋回させる方法が提案されている。
さらに、特許文献4には、吐出孔を放射方向に対して傾けて設置し、浸漬ノズルを上下2つのパーツとし、下側のノズルが鉛直軸に回転させる構造をとる方法が提案されている。
すなわち、前述の特許文献1及び2の場合、実験の結果、旋回流は得られるものの安定した旋回流は得られず、旋回流の発生/消失を繰り返すことになっていた。
また、前述の特許文献3の構成の場合、浸漬ノズルが容易に回転するように、金属部品を介してベアリングと接触する構造となっており、接続する耐火物とのシール性に問題があった。
また、前述の特許文献1から4の何れ場合も、こうした従来の提案構造では旋回する流れが不安定で且つ流速が遅く、介在物や気泡が凝固シェルに捕捉されるのを防ぐには充分な効果が得られていなかった。また、丸ビレットのような円形断面をもつ鋳造に対しては更に効果が得られなかった。
0.2≦(a-ri)/t かつ (b-ri)/t≦0.9
とする構成である。
また、前記浸漬ノズルのノズル底に円形或いは多角形の底孔を有し、前記底孔の開孔面積をSbとし、底孔も含めた全ての開孔部の面積の総和をStとした際、前記吐出孔流路の開孔面積と前記底孔の開孔面積を合計した総開孔面積をStとした際、前記Sb/Stが0~0.4とした構成である。
すなわち、ノズル孔を有する浸漬ノズルの円筒側面に2つ以上の吐出孔流路を持ち、前記浸漬ノズル使用時の水平断面における前記吐出孔流路の第1、第2内面側壁及び第1、第2外面側壁が、内側屈折点及び外側屈折点によって屈折して形成された直線によって構成されたことにより、他の設備に変更を加えることなく、浸漬ノズルの吐出孔流路の形状改善のみによってモールド内に安定した溶鋼の旋回流を発生させ、鋳片品質の向上に寄与することができる。
尚、本発明による溶融金属連続鋳造用の浸漬ノズルを開発するまでの課程を含めて、まず、説明する。
一般に、電磁撹拌装置をはじめとして、製造設備に特に変更を加えずにモールド内に安定した旋回流を得るためには、浸漬ノズルから吐出孔を通って流出する吐出流が、(1)浸漬ノズルの中心軸から見て放射方向に対して一定量傾くこと、(2)上記吐出流の状態が安定して継続されること、の2点が重要である。このような視点から様々な吐出孔形状を考案し、水モデル実験を実施して各孔形状の評価を行い、本発明による浸漬ノズルの開発に至ったものである。
まず、図11のように、文献1~4にあるようなノズル孔1の接線方向に吐出孔流路2を設けた形状、図12の文献1と3にあるようなノズル孔1の接線方向に吐出孔流路2を設けて湾曲させた形状を用いて旋回流が生じるかどうかを検討したが、旋回流は得られるものの、安定した旋回流は得られず、旋回流の発生/消失を繰り返した。
そこで、様々な形状を検討し、図2に示したように、吐出孔流路2を途中でくの字型に屈折させ鍵型に曲げた場合、モールド全体に浸漬ノズル3を中心軸とした旋回流が安定的に形成されることを発見した。
さらに、図13のように吐出孔流路2の内側のみを屈折した場合と、図14のように外側のみを屈折させた場合について実験を行ったが、この場合は十分な旋回流が得られなかった。
図9は、十分な旋回流が得られた図2の吐出孔流路2の断面の場合の吐出流速測定結果である。横軸は、時間変化を示し、縦軸は10秒間毎の平均流速の相対値を示し、上で高く、下で低い状態を示す。前記吐出孔流路2の上下方向での流速を比較すると、下側のBとDで大きいが、これは浸漬ノズル3内を上方から下方へ流下する流れの影響による。一方、流速には時間変化が見られるが、浸漬ノズル3直上にある周知のスライディングプレートで流量制御するため、浸漬ノズル3内で少し偏った流れとなり、また、流速が変化することによる。吐出孔流路2の同一水平面上(DとB, CとA)の流速値を比較すると、屈折の内側B、A側の方が、外側C、D側と比べて常に遅くなっていた。
それに対し図10は、十分な旋回流が得られなかった図12の吐出孔流路2の断面の場合の吐出流速測定結果である。吐出孔流路2の同一水平面上(DとB, CとA)の流速値を比較すると吐出孔流路2の外側の流速D、Cと内側の流速B、Aとの差が殆どなく、時折湾曲の内側(B、A)の方が流速が速くなる逆転現象が認められた。計測中のモールド内は、旋回流の発生/消失を繰り返す不安定な状態であった。
本発明による溶融金属連続鋳造用の浸漬ノズルは、前述の発見と解析によって得られたものである。
尚、吐出孔流路2は浸漬ノズル3下部で回転対称の位置に設置することが好ましい。こうすることで吐出孔流路2からの流れによって旋回運動を継続させることができる。また、吐出孔流路2の設置個数は2~4が好ましいが、それ以上とすることも可能である。
本発明において技術的に最も重要な点は内側屈折点5で吐出孔流路2が湾曲ではなく屈折した構造を持ち、流れが壁面から剥離して澱み部が発生する点にある。このため浸漬ノズル3使用時の水平断面におけるその吐出孔流路2の両側面は、実質的に屈折した直線によって構成されていることが望ましい。内面側の第1、第2内面側壁6、7を屈折させることで内側屈折点5より下流側で渦6aを作り出し、また流路外側の流速を上昇させることができる。また、外面側の第1、第2外面側壁10,11を屈折させることで、流れの方向をノズル孔1の中心から見た放射方向に対して傾いた方向に向けることができ、旋回流ができる。これらを組み合わせることで、安定した旋回流を生むものである。
従って、モールド内での旋回流を生成させるためには、吐出孔流路2内流速に定常的な偏りを発生させることが必要であり、そのためには、流路2の両側の壁がそれぞれ同じ方向に屈折していること、屈折角度がある一定範囲の中であることが重要である。図13のように内側のみが屈折し、反対側が直線である場合、流れは直線の壁面に沿ってノズル孔1からほぼ放射状に吐出され、モールド内に旋回流を発生させることが出来ない。また図14のように外側のみが屈折している場合にもモールド内に充分な旋回流を発生させることが出来ない。
前記吐出孔流路2の内側屈折点5および外側の外側屈折点9では、製造上の便宜を図るために小さなRを付けても良い。但し特に内側においては、Rが大きすぎると屈折流路から湾曲流路に近付き、充分な旋回流が得られなくなる。具体的にはRは5mm以下、より好ましくは3mm以下である。また、内側と外側のRは曲率が異なっても差し支えない。
(a-ri)/tが0.2未満の場合、浸漬ノズル3のノズル孔1から吐出孔流路2へ向かった流れが十分には発達せず、そのため、屈折点5,9より下流側での渦の成長も十分には起こらない。そのため、十分な旋回流が得られない。(a-ri)/tの最大値は特には規定されないが、後述の吐出孔流路2の形状によって決定される。
前述吐出孔流路2を浸漬ノズル3側面に設けるのに加えて、図15で示すように、ノズル底面に底孔17を設けても良い。
鋳型断面積と浸漬ノズル3内の溶鋼通過量との関係から、浸漬ノズル3内の溶鋼通過量が多くて側面に設けた吐出孔流路2からの吐出流が鋳型断面積との比較で多すぎる場合、旋回流を生む吐出流が強くなりすぎてメニスカス変動が大きくなり、鋳造が不安定になる場合がある。この場合、底孔17を設け、旋回流を与えるに必要な流量だけ側面の吐出孔流路2から流出させ、残りの溶鋼流を、前記底孔17からモールド下流へ導入させることで安定的な旋回状態とメニスカス変動の抑制の両立を図ることが出来る。
前記底孔17の開孔面積をSbとし、側面に設けた吐出孔流路2の開孔面積と、底孔17の開孔面積を合計した総開孔面積Stとした際、上記底孔17からの溶鋼流出量Sb/Stに関係し、その値が大きければ、ノズル内の溶鋼通過量に対する底孔17から流出する溶鋼量の比率も多くなる。また、Sb/Stは、0~0.4とすることが望ましい。より好ましくは0.1~0.35である。
前記底孔17の底孔壁17aに平行な方向の断面における形状は円形であることを基本とするが、多角形形状でも構わない。また、底孔壁17aに垂直な断面方向での形状は、直線をなす場合、曲線をなす場合、複数の直線または曲線を組み合わせる場合、中央部で凸となる形状などを選択できる。
更には、図示していないが、複数個の底孔17を開けることも可能である。この場合、前記Sbはその底孔17の面積の総和となる。また、複数個開けた底孔17の吐出方向をノズル軸に対して傾斜を持たせたり、さらに吐出方向がノズル軸と交わらないように設けることも可能である。
実際の設備と同様のスケールの水モデルシミュレーション設備を用い、表1に表わされる浸漬ノズル3を使用した際に、安定して旋回流の発生を実現できるか否かを評価した。
浸漬ノズル3の水モデルはφ200mmの丸ビレット連鋳機を想定した水モデルとし、浸漬ノズル3は内径35mm、外径75mm、ノズルの肉厚20mm、吐出孔の出口断面を24mm×22mm、吐出孔数2個、鋳込み引き抜き速度を1.5m/分とした条件で行った。
旋回流の評価は以下のように行った。すなわち、3分間実験し、その間モールド内に定常的に旋回流が発生していた場合を旋回流速と安定性の観点から評価した。旋回流速は、十分大きい場合は“良好”、旋回流はあるがあまり大きくない場合は“やや不十分”、発生しない場合は“発生せず”とした。また、安定については、安定して旋回流が得られた場合を“良好”とし、回流が発生/消失を繰り返す場合は“不安定”とし、発生しない場合は“発生せず”とした。
種々の吐出孔流路2の形状を用いて水モデル試験を実施したが、その特徴は以下の通りである。
流路途中で屈折点がある場合、全てR5とした。試験結果について表1に示す。なお各吐出孔形状の特徴については、下記のように表現した。
1. 接線:吐出孔経路が内径の接線方向の直線で形成される図11の形状で文献1~4に例示されている形状である。
2. 湾曲:使用時の鉛直方向から見た場合に吐出孔経路が屈曲している図12に示した形状で、文献1,3に例示されている形状である。
3. 内側のみ屈折: 吐出孔経路の側壁が内側のみ屈折し、反対側は直線で形成される、図13に示した形状である。
4. 外側のみ屈折: 吐出孔経路の側壁が外側のみ屈折し、反対側は直線で形成される、図14に示した形状である。
5. 屈折:吐出孔流路2の側壁が途中で両壁が同一方向へ屈折する図2に示した形状である。
文献1~4に記載されているような接線形状、および文献1, 3に記載されている湾曲形状の場合、旋回流は流速が弱い上に発生と消失を繰り返し、モールドは不安定な状況であった(比較例1,2)。吐出孔経路の内側のみが屈折(比較例3~5)、外側のみが屈折(比較例6~9)の場合は、旋回流は発生しなかった。吐出孔流路2両側が同じ方向へ屈折している形状で、βが15~85°であり、ノズル中心から屈折点5,9までの距離a,bがそれぞれ0.2≦(a-ri)/t, (b-ri)/t≦0.9の範囲内である場合には、充分な速度をもって、安定した旋回流が得られたが(発明品1~7)、βが範囲内でも屈折点までの距離が範囲外である場合(比較例10,12,13)や、βが範囲外の場合(比較例11,14,15)は安定して旋回流は存在するものの、あまり大きくはなかった。
全てスループット条件において、旋回流は発生したが、スループット条件が0.2ton/minの場合は、旋回流速が遅く、不十分な状態であった。0.4、1.8ton/minの条件では、良好な旋回状態を得られたが、2.2ton/minの場合には、メニスカス変動が激しくなることで不安定な状態となった。
Claims (4)
- ノズル孔(1)を有する浸漬ノズル(3)の円筒側面に2つ以上の吐出孔流路(2)を持ち、前記浸漬ノズル(3)使用時の水平断面における前記吐出孔流路(2)の第1、第2内面側壁(6,7)及び第1、第2外面側壁(10,11)が、内側屈折点(5)及び外側屈折点(9)によって屈折して形成された直線によって構成されたことを特徴とする溶融金属連続鋳造用の浸漬ノズル。
- 前記浸漬ノズル(3)の吐出孔流路(2)の内側で前記第1内面側壁(6)及び第1外面側壁(10)がなす2本の直線と前記ノズル孔(1)の外縁(1c)が交わる第1、第2交点(13,14)を結ぶ直線(1a)と、前記直線(1a)と直交し前記ノズル孔(1)の孔中心(P)を通る第1中心線(15)とがなす第1角度(α)が、45~135°であることを特徴とする請求項1に記載の溶融金属連続鋳造用の浸漬ノズル。
- 前記浸漬ノズル(3)の厚みをtとし、前記ノズル孔(1)の孔中心(P)から前記内側屈折点(5)までの距離をaとし、前記孔中心(P)から前記外側屈折点(9)までの距離をbとし、riを前記ノズル孔(1)の半径とした際、
0.2≦(a-ri)/t かつ (b-ri)/t≦0.9
とすることを特徴とする請求項1又は2に記載の溶融金属連続鋳造用の浸漬ノズル。 - 前記浸漬ノズル(3)のノズル底(17b)に円形或いは多角形の底孔(17)を有し、前記底孔(17)の開孔面積をSbとし、前記吐出孔流路(2)の開孔面積と前記底孔(17)の開孔面積を合計した総開孔面積をStとした際、前記Sb/Stが0~0.4であることを特徴とする請求項1ないし3の何れかに記載の溶融金属連続鋳造用の浸漬ノズル。
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US14/389,900 US9573189B2 (en) | 2012-04-26 | 2013-04-11 | Submerged nozzle for continuous casting apparatus |
EP13780562.8A EP2842658A4 (en) | 2012-04-26 | 2013-04-11 | INTEGRATED PIPE OF A CONTINUOUS CASTING DEVICE |
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CN108393479A (zh) * | 2018-04-18 | 2018-08-14 | 宜兴市龙宸炉料有限公司 | 一种可延长上水口使用寿命的中间包水口座砖 |
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TWI548471B (zh) * | 2014-04-28 | 2016-09-11 | 中國鋼鐵股份有限公司 | 型鋼連續鑄造之注嘴 |
EP3056304A1 (en) * | 2015-02-16 | 2016-08-17 | Uvån Holding AB | A nozzle and a tundish arrangement for the granulation of molten material |
CN108247033B (zh) * | 2018-01-17 | 2020-07-21 | 武汉科技大学 | 一种连铸中间包用旋流上水口 |
CN108480609B (zh) * | 2018-03-30 | 2020-02-11 | 东北大学 | 一种连铸防堵塞浸入式水口 |
KR102367022B1 (ko) * | 2020-11-23 | 2022-02-23 | 동의대학교 산학협력단 | 치아 착색기 카트리지 모듈 |
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