JP2010099688A - Dipping nozzle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dipping nozzle which can supply a molten steel into a mold at a predetermined flow rate stably from immediately after the start of pouring, can prevent the occurrence of breakout of a cast strip due to a fluctuation of a pouring amount in an early stage of casting and can improve productivity. <P>SOLUTION: A dipping nozzle 10 has a nozzle part 12 that supplies a molten steel 1 within a tundish 31 from the tundish into a pouring basin while regulating the flow rate of the molten steel 1 by a stopper rod 32. The inner diameter dm in the nozzle part 12 satisfies formula (1). In formula (1), dm is the inner diameter of the nozzle part 12 at a distance Z from the upper part of the nozzle part 12; C is the flow coefficient of a flow rate regulating means; Di is the inner diameter of the upper part of the nozzle part 12; H1 is the level (height) of the molten steel from the upper part of the nozzle part at the beginning of casting; and Z is the distance from the upper part of the nozzle part 12. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a submerged nozzle that supplies molten steel in a tundish to a hot water pool using a continuous casting machine.

  In the continuous casting machine, the molten steel is transferred from the ladle to the tundish, and from this tundish, the hot water pool in the mold (for example, the twin rolls with the circumferential surfaces facing each other and the two rolls are arranged at both ends. A nozzle is used to inject into a space formed by a weir and a mold. Examples of the nozzle include an open nozzle in which the tip (lower end) of the nozzle is not immersed in the molten steel in the mold, and an immersion nozzle in which the discharge port at the tip of the nozzle is immersed in the molten steel in the mold.

  The open nozzle has a small flow rate of molten steel and is used in continuous casting of billets, continuous casting of beam blanks, etc., and its inner diameter is as small as about 20 mm, and the nozzle length is as short as about 100 mm. . On the other hand, the immersion nozzle has a large flow rate of molten steel and is used for continuous casting of slabs. Its inner diameter is about 50mm to 120mm, which is larger than the open nozzle, and its nozzle length is about 700mm to 1200mm. The shape is longer than that of the nozzle.

  The above-described open nozzle is disclosed in Patent Document 1, for example. This Patent Document 1 describes an open nozzle in which the inner wall of the nozzle tip is formed in a tapered shape. By adopting such a shape, air entrainment (generation of negative pressure) in the vicinity of the lower end of the nozzle is prevented, wear of the nozzle is suppressed, and a long life is achieved.

Japanese Patent No. 3639513 (for example, see FIG. 1)

  In conventional immersion nozzles, there is no taper in the height direction inside the immersion nozzle, and at the beginning of pouring, the pouring flow that contracts inside the nozzle does not contact the wall surface inside the nozzle. The interior is not filled with molten steel. In the state where the nozzle is not filled with molten steel, the head acting on the molten steel is lower than the state where the nozzle is filled with molten steel. For this reason, in the initial stage of pouring, in which the inside of the nozzle is not filled with molten steel, the amount of pouring is smaller than in the state in which molten steel is filled in the nozzle. As a result, a difference occurs between the predicted value of the molten steel pouring amount calculated on the assumption that the nozzle is filled with molten steel and the actual pouring amount, and the predetermined molten steel amount is stored in the hot water pool in the mold. There was a difference from the predicted value in the time until accumulation. Due to the deviation from the predicted value, for example, when drawing of the slab from the mold is started before a predetermined amount is accumulated in the hot water pool, the surface of the slab is not sufficiently cooled, and the solidified part inside the slab As a result, a slab with a small thickness was pulled out, resulting in breakage of the slab called breakout, which caused great inconvenience for production. It should be noted that the time during which the nozzle is filled with molten steel at the beginning of casting varies greatly between prediction and actual casting, and the prediction accuracy is low. Therefore, even if the time for filling the inside of the nozzle with molten steel is estimated, and the amount of pouring is predicted in consideration of the fluctuation of the head acting on the molten steel, the prediction accuracy is low, and the prediction of the time when a predetermined amount is accumulated in the hot water pool The accuracy is also low.

  Even if the open nozzle described in Patent Document 1 is applied to the immersion nozzle, there is a straight portion inside the nozzle, and this portion does not contact the molten steel at the beginning of pouring. For this reason, the inside of the nozzle is not filled with molten steel at the beginning of pouring, the head acting on the molten steel is lower than the state in which the nozzle is filled with molten steel, and compared to the state in which the nozzle is filled with molten steel. The amount of hot water decreases. Therefore, immediately after the start of pouring, the amount of pouring supplied from the tundish cannot be predicted appropriately.

  Therefore, the present invention has been proposed in view of the problems described above, and immediately after the start of pouring, the molten steel is stably supplied from the tundish to the sump portion at a flow rate corresponding to the state in which the nozzle is filled with molten steel. An object of the present invention is to provide an immersion nozzle capable of effectively improving productivity.

但し、（１）式において、ｄｍがノズル部の上部からの距離Ｚにおけるノズル部の内径であり、Ｃが流量調整手段の流量係数であり、Ｄｉがノズル部の上部における内径であり、Ｈ１が鋳造開始時におけるノズル部の上部からの溶鋼レベル（高さ）であり、Ｚがノズル部の上部からの距離である。 The immersion nozzle according to the first invention for solving the above-described problem is
An immersion nozzle for supplying molten steel in a tundish to the hot water reservoir from the tundish by adjusting the flow rate of the molten steel by a flow rate adjusting means,
The inner diameter dm of the nozzle portion arranged downstream of the flow rate adjusting means satisfies the following expression (1).

However, in the formula (1), dm is the inner diameter of the nozzle portion at a distance Z from the upper portion of the nozzle portion, C is the flow coefficient of the flow rate adjusting means, Di is the inner diameter at the upper portion of the nozzle portion, and H1 is It is the molten steel level (height) from the upper part of the nozzle part at the start of casting, and Z is the distance from the upper part of the nozzle part.

  According to the immersion nozzle according to the present invention, the molten steel in the tundish is an immersion nozzle that adjusts the flow rate of the molten steel by the flow rate adjusting means and supplies the molten steel from the tundish to the hot water reservoir, downstream of the flow rate adjusting means. When the inner diameter dm of the nozzle portion arranged in the nozzle satisfies the above equation (1), the inner diameter of the nozzle portion is set smaller than the horizontal cross-sectional area when the molten steel naturally falls in the atmosphere, and pouring starts. Immediately after that, the inside of the nozzle can be reliably filled with molten steel. As a result, the flow rate of the molten steel inside the nozzle portion is stabilized at a flow rate corresponding to the state in which the inside of the nozzle is filled with molten steel. Therefore, it becomes possible to suppress a breakout that occurs due to a low prediction accuracy of the pouring amount, and it is possible to effectively improve productivity.

  Below, the best form for implementing the immersion nozzle which concerns on this invention is demonstrated concretely based on an Example.

An immersion nozzle according to a first embodiment of the present invention will be described with reference to FIG.
FIG. 1 is an explanatory diagram of an immersion nozzle according to the first embodiment of the present invention.

  As shown in FIG. 1, the immersion nozzle 10 according to the first embodiment of the present invention is provided in communication with the bottom 31a of the tundish 31 in which the molten steel 1 is stored. A trumpet portion 11 on which a lower end portion 32a of a stopper rod (flow rate adjusting means) 32 is seated is provided at the opening of the upper end portion of the immersion nozzle 10 in the bottom portion 31a of the tundish 31. The lower end portion 32a of the stopper rod 32 is formed in an arc shape that protrudes downward in FIG. The trumpet portion 11 is formed in an arc shape that protrudes toward the axis (not shown) of the immersion nozzle 10. Therefore, when the lower end portion 32a of the stopper rod 32 is seated (contacted) on the trumpet portion 11, the supply of the molten steel 1 from the tundish 31 to the immersion nozzle 10 is stopped.

  The immersion nozzle 10 includes a bottomed cylindrical nozzle portion 12 extending in the vertical direction. That is, a flow path (inside the nozzle) 13 for supplying the molten steel 1 from the tundish to the puddle portion is formed in the nozzle portion 12, and a bottom wall portion 14 that closes the lower end portion is formed at the lower end portion of the nozzle portion 12. Is done. A discharge port 15 is formed in the vicinity of the bottom wall portion 14 of the nozzle portion 12. There are also nozzles in which a discharge port is provided in the bottom wall portion 14 or an immersion nozzle that uses the portion as a discharge port without using the bottom wall portion 14. The discharge ports 15 are formed at two places in FIG. In addition, as a horizontal cross-sectional shape of the nozzle part 12, although circular is common, shapes, such as elliptical shape or a square shape, are also mentioned.

  The nozzle portion 12 described above has an inner diameter dm of, for example, about 50 mm to 120 mm, and a nozzle length (a distance from the upper end of the inner wall 12a continuous to the lower end portion 11a of the trumpet portion 11 to the bottom wall portion 14), for example, 700 mm to The shape is about 1200 mm.

  The inner wall 12a of the nozzle part 12 described above is a nozzle from the upper part of the nozzle part 12 (the upper end part of the inner wall 12a continuous with the lower end part 11a of the trumpet part 11) toward the lower part (the lower edge part of the discharge port 15). The inner diameter dm of the part 12 changes continuously, and the inner diameter dm of the nozzle is set smaller than the horizontal cross-sectional area when the molten steel 1 naturally falls in the atmosphere. A tapered portion 20 is formed over the entire region in the height direction inside the nozzle portion 12, and the inclination angle of the tapered portion 20 with respect to the horizontal cross section is set larger toward the lower portion of the nozzle portion 12.

  Specifically, the inner diameter dm of the nozzle portion 12 described above is formed to satisfy the following expression (1). However, in the following formula (1), dm is the inner diameter of the nozzle portion 12 at a distance Z from the upper portion of the nozzle portion 12 (the upper end portion of the inner wall 12a continuous with the lower end portion 11a of the trumpet portion 11), and C is the flow rate. It is a flow coefficient of the adjusting means, Di is an inner diameter at the upper part of the nozzle part 12, H1 is a molten steel level (height) from the upper part of the nozzle part 12 at the start of casting, and Z is an upper part of the nozzle part 12 ( This is the distance from the lower end 11 a) of the trumpet 11. When a stopper rod is used as the flow rate adjusting means, as shown in FIG. 1, the flow rate coefficient is set to a predetermined value according to the distance between the tip end portion 32 a of the stopper rod 32 and the trumpet portion 11. Thus, when the inner diameter dm of the nozzle portion 12 satisfies the following expression (1), the inner diameter dm of the nozzle portion 12 is set smaller than the horizontal cross-sectional area when the molten steel 1 naturally falls in the atmosphere. The

  Therefore, the inner wall 12a of the nozzle portion 12 is tapered, and the inclination angle of the tapered portion 20 with respect to the horizontal cross section of the nozzle portion 12 increases from the upper end portion to the lower end portion and from the upper end portion to the lower end portion. The lower part is set larger. In this way, by changing the shape of the inner wall 12a of the nozzle portion 12 into an arc shape, the molten steel does not contact the nozzle at the beginning of pouring due to the influence of the contraction of the molten steel, and the nozzle is not filled with the molten steel. Is suppressed. That is, before the start of pouring, the tip 32a of the stopper rod 32 is in contact with the trumpet 11, and the molten steel 1 is stored in the tundish 31 at the molten steel level H2. Subsequently, the stopper rod 32 is separated from the trumpet portion 11, and the molten steel 1 is filled into the nozzle portion at the moment when the pouring flow reaches the bottom wall portion 14, and the molten steel 1 in the tundish 31 and the molten steel in the immersion nozzle 10 are filled. 1 (molten steel 1 from the trumpet portion 11 to the center position in the vertical direction of the discharge port 15) acts on the molten steel supplied from the discharge port to the hot water pool portion. Thereby, the influence of the head fluctuation on the flow rate of the molten steel 1 in the nozzle does not occur, the amount of pouring is stabilized at the flow rate corresponding to the state in which the nozzle is filled with the molten steel, and the prediction accuracy of the pouring amount is increased. Therefore, a predetermined amount of molten steel 1 can be accumulated in a predetermined time predicted in advance in a hot water reservoir (not shown) disposed below the immersion nozzle 10. Therefore, the drawing start time of the molten steel 1 in the hot water pool portion can be set to be constant, breakout that occurs due to low prediction accuracy of the pouring amount can be suppressed, and productivity can be effectively improved.

  Therefore, according to the immersion nozzle 10 which concerns on a present Example, when the internal diameter dm of the nozzle part 12 satisfy | fills said (1) Formula, the internal diameter of the nozzle part 12 is when the molten steel 1 falls naturally in air | atmosphere. Thus, the molten steel 1 can be reliably filled into the nozzle portion immediately after the start of pouring. As a result, the flow rate of the molten steel 1 supplied from the tundish 31 to the hot water reservoir is stabilized from the beginning of pouring at a flow rate predicted in advance. As a result, a predetermined amount of molten steel 1 can be stored in the hot water reservoir in a predetermined time. Therefore, the time until a predetermined amount of molten steel accumulates in the hot water pool in the mold is in good agreement with the predicted value and the actual measured value at the time of casting, and the occurrence of breakout when the slab is started is suppressed. Thus, productivity can be effectively improved.

  In the above description, the stopper rod is used as the flow rate adjusting means. However, a slide gate nozzle can be used instead of the stopper rod. Even when this slide gate is used, the same effect as the immersion nozzle 10 according to the first embodiment described above is obtained.

An immersion nozzle according to a second embodiment of the present invention will be described with reference to FIG.
FIG. 2 is a graph showing the relationship between the distance from the nozzle upper part and the inner diameter of the nozzle in the immersion nozzle according to the second embodiment of the present invention. In FIG. 2, the inner diameter Di at the top of the nozzle is set to 100 mm, the molten steel level (height) from the top of the nozzle at the start of pouring is set to 500 mm, and a stopper rod is used as the flow rate adjusting means. The distance from is plotted every 100 mm.

  In the submerged nozzle according to the second embodiment of the present invention, a taper portion is formed over the entire region in the height direction inside the nozzle portion, and the taper portion is constituted by first to tenth taper portions. ing.

  Here, the relationship between the distance Z from the nozzle upper portion (the upper portion of the nozzle) in the nozzle portion and the cylindrical nozzle diameter (inner diameter of the nozzle portion) dm, as shown in FIG. 2, when Z is 100 mm, With respect to the axis, θ11 is 3.4 ° (the inclination angle with respect to the horizontal section is 90 minus θ11). Similarly, when Z is 200 mm, 300 mm, 400 mm, 500 mm, 600 mm, 700 mm, 800 mm, 900 mm, 1000 mm, θ12 (the inclination angle with respect to the horizontal section is 90 minus θ12) and θ13 ( The tilt angle with respect to the horizontal section is 90 minus θ13), θ14 (the tilt angle with respect to the horizontal section is 90 minus θ14), θ15 (the tilt angle with respect to the horizontal section is 90 minus θ15), θ16 (the tilt angle with respect to the horizontal section is 90 minus θ16), θ17 (the inclination angle with respect to the horizontal section is 90 minus θ17), θ18 (the inclination angle with respect to the horizontal section is 90 minus θ18), θ19 (the inclination angle with respect to the horizontal section is 90 minus θ19), θ20 (the inclination angle with respect to the horizontal section is 90 minus θ20) )

  Therefore, the inner wall of the nozzle portion is tapered, and the inclination angle with respect to the horizontal cross section at the tapered portion increases from the upper end portion toward the lower end portion and from the upper end portion toward the lower end portion as the lower portion of the nozzle portion. Is done. In this way, by changing the shape of the inner wall of the nozzle portion in stages, the occurrence of a state in which the nozzle and the molten steel do not contact with each other due to the influence of the contraction of the pouring flow inside the nozzle portion at the beginning of pouring is suppressed. . That is, before the start of pouring, as shown in FIG. 1, the tip 32a of the stopper rod 32 is in contact with the trumpet 11, and the molten steel 1 is stored in the tundish 31 at the molten steel level H2. . Subsequently, the stopper rod 32 is separated from the trumpet portion 11, and the molten steel 1 is filled into the nozzle portion at the moment when the pouring flow reaches the bottom wall portion 14, and the molten steel 1 in the tundish 31 and the molten steel in the immersion nozzle 10 are filled. 1 (molten steel 1 from the trumpet 11 to the central position in the vertical direction of the discharge port 15) acts on the molten steel supplied from the discharge port. Thereby, the head which acts on the molten steel supplied from the discharge port 15 of the nozzle part 12 is stabilized from the beginning of pouring, and the flow rate agrees well with the predicted flow rate assuming the state in which the inside of the nozzle is filled with molten steel. Stabilize. Therefore, a predetermined amount of molten steel 1 can be stored in the hot water reservoir in a predetermined time. Therefore, when the drawing of the slab is started, it is possible to suppress the breakout that occurs due to the low prediction accuracy of the pouring amount, and the productivity can be improved.

  Therefore, according to the immersion nozzle which concerns on a present Example, molten steel can be reliably filled in a nozzle part immediately after the start of pouring. As a result, the head acting on the molten steel supplied from the discharge port is stabilized from the beginning of pouring, and the flow rate thereof also agrees well with the value calculated on the assumption that the nozzle portion is filled with molten steel. Therefore, the time required for a predetermined amount of molten steel to accumulate in the hot water pool in the mold is in good agreement between the predicted value and the actual measured value during actual casting, and the prediction accuracy of the pouring amount when the slab starts being drawn is The breakout of the slab generated by being low is suppressed, and the productivity can be improved.

  In the above description, the description has been given using the immersion nozzle including the nozzle portion in which ten taper portions are formed. However, an immersion nozzle including at least two taper portions such as two, three, or four may be used. is there. It is also possible to use an immersion nozzle in which the tapered portion is formed equally with respect to the nozzle length. When a plurality of taper portions are provided and the length of the plurality of taper portions is a predetermined ratio, for example, three taper portions are provided, the first taper portion, the second taper portion, and the third taper portion An immersion nozzle formed with a length ratio of 1: 2: 3 is also possible. Even such immersion nozzles have the same effects as the immersion nozzles according to the second embodiment described above.

  The immersion nozzle according to the present invention can stably supply molten steel from the tundish to the puddle immediately after the start of pouring at a predetermined flow rate, preventing the occurrence of breakout at the beginning of casting due to fluctuations in the pouring amount. Since this is possible, productivity can be improved. Therefore, it can be used extremely beneficially in the steel industry.

It is explanatory drawing of the immersion nozzle which concerns on the 1st Example of this invention. It is a graph which shows the relationship between the distance from the nozzle upper part in the immersion nozzle which concerns on the 2nd Example of this invention, and the internal diameter of a nozzle.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Molten steel 10 Immersion nozzle 11 Trumpet part 11a Lower end part 12 Nozzle part 12a Inner wall 13 Flow path 14 Bottom wall part 15 Discharge port 20 Taper part 31 Tundish 31a Bottom part 32 Stopper rod 32a Tip part

Claims (1)

An immersion nozzle for supplying molten steel in a tundish to the hot water reservoir from the tundish by adjusting the flow rate of the molten steel by a flow rate adjusting means,
An immersion nozzle characterized in that an inner diameter dm of a nozzle portion arranged downstream of the flow rate adjusting means satisfies the following expression (1).

However, in the formula (1), dm is the inner diameter of the nozzle portion at a distance Z from the upper portion of the nozzle portion, C is the flow coefficient of the flow rate adjusting means, Di is the inner diameter at the upper portion of the nozzle portion, and H1 is It is the molten steel level (height) from the upper part of the nozzle part at the start of casting, and Z is the distance from the upper part of the nozzle part.

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