JP5366991B2 - Immersion nozzle for continuous casting - Google Patents

Description

  The present invention relates to an immersion nozzle for continuous casting.

  The continuous casting immersion nozzle is for flowing molten steel from the tundish into the mold, and is disposed between the tundish mold. The molten metal surface of the mold is detected by a sensor, and when the molten metal surface falls, a large amount of molten steel flows in, and when the molten metal surface rises, the amount of molten steel flowing in is reduced.

  Therefore, if vertical fluctuations not caused by the inflow amount such as undulations occur on the molten metal surface, good casting speed control cannot be performed. Such swell is caused by the occurrence of uneven flow in the nozzle when the molten steel falls and flows in, and different amounts of discharge from the left and right discharge ports (single flow phenomenon). For example, as shown in FIGS. 7 and 8, a continuous casting immersion nozzle 30 provided with annular steps 32 and 33 over the entire circumference of the inner surface 31 of the nozzle inner hole is used (Japanese Patent Laid-Open No. 11-123509). ). These annular steps 32 and 33 act to suppress the drift by guiding the molten steel to the center of the nozzle inner hole 34.

  However, if an annular step is provided over the entire circumference, the molten steel concentrates at the center of the nozzle bore and becomes too fast, which in turn causes the fluctuation of the molten metal surface.

Japanese Patent Laid-Open No. 11-123509

  Accordingly, the inventors of the present application have conducted a keen study on a level difference that can be uniformly discharged from the right and left discharge ports and have little fluctuation in the molten metal surface, and as a result, the present invention has been completed. That is, an object of the present invention is to provide an immersion nozzle for continuous casting that can alleviate the inflow speed of molten steel, can equalize the discharge amount from the left and right discharge ports, and has less fluctuation of the molten metal surface due to swells and the like. It is in.

What solves the above-described problems includes a nozzle body, a nozzle inner hole provided in the nozzle body for flowing molten steel , and a pair of discharge ports provided symmetrically facing the lower portion of the nozzle body. has the nozzle holes, to face provided symmetrically on the top of the pair of discharge ports, it has a pair of stepped continuous within the 80~250mm over and below the meniscus, vomiting outlet Is a continuous casting immersion nozzle characterized in that no step is provided .

  It is preferable that a pair of second steps provided opposite to each other is formed on top of the pair of steps in the nozzle inner hole. A second step formed in an annular shape may be provided above the pair of steps in the nozzle inner hole. The pair of steps is preferably formed within a range of 45 to 135 ° on the inner periphery of the nozzle inner hole. The pair of steps is preferably formed within a range of 5 to 15 mm in thickness. It is preferable that the pair of steps are respectively formed within a range of 80 to 250 mm in length in the vertical direction.

According to the continuous casting nozzle described in claim 1, the flow rate of the molten steel can be reduced, the discharge amount from the left and right discharge ports can be made more uniform, and vertical fluctuations not caused by undulation or inflow amount on the molten metal surface. Fewer nozzles for continuous casting can be constructed.
According to the nozzle for continuous casting described in claim 2, it becomes an immersion nozzle for continuous casting that exhibits the effect of claim 1 above.
According to the nozzle for continuous casting described in claim 3, it becomes an immersion nozzle for continuous casting that can further suppress the drift of molten steel.

It is the longitudinal cross-sectional schematic which longitudinally cut off one Example of the immersion nozzle for continuous casting of this invention by the non-discharge port side. It is the longitudinal cross-sectional schematic which longitudinally cut the immersion nozzle for continuous casting shown in FIG. 1 by the discharge outlet side. It is the longitudinal cross-sectional schematic which longitudinally cut | disconnected the other Example of the immersion nozzle for continuous casting of this invention by the non-discharge port side. It is the longitudinal cross-sectional schematic which longitudinally cut the immersion nozzle for continuous casting shown in FIG. 3 at the discharge outlet side. It is a perspective schematic diagram for demonstrating a hot_water | molten_metal surface fluctuation | variation test. It is the longitudinal cross-sectional schematic for demonstrating the comparative example of the immersion nozzle for continuous casting in a molten metal surface variation test. It is the longitudinal cross-sectional schematic which longitudinally cut the conventional immersion nozzle for continuous casting at the non-discharge port side. It is the longitudinal cross-sectional schematic which longitudinally cut the immersion nozzle for continuous casting shown in FIG. 7 by the discharge outlet side.

  In the present invention, by forming a pair of steps in the nozzle inner hole facing the upper portions of the pair of discharge ports and continuing up and down the meniscus, the molten steel reaching the vicinity of the meniscus is formed on the discharge port side. Guided into the mold along the surface of the step that reduces the diameter of the nozzle inner hole, and on the other side of the discharge port where no step is provided, it flows into the mold along the surface of the nozzle hole. Since the inflow speed of the molten steel is relaxed compared to the case where the flow rate is reduced, the pair of steps are provided at opposite positions (symmetric positions with respect to the central axis of the nozzle body). The amount of discharge was made uniform, and a continuous casting immersion nozzle with less fluctuation of the molten metal surface due to swell and the like was realized.

The continuous casting nozzle of the present invention will be described with reference to one embodiment shown in FIG. 1 or FIG.
The continuous casting nozzle 1 of this embodiment includes a nozzle body 2, a nozzle inner hole 3 provided in the nozzle body 2 for flowing molten steel, and a pair of discharges provided facing the lower portion of the nozzle body 2. The nozzle inner hole 3 has a pair of steps 5a and 5b which are provided opposite to the upper portions of the pair of discharge ports 4a and 4b and are continuous across the upper and lower sides of the meniscus A. Yes. Hereinafter, each configuration will be described in detail.

  The nozzle body 2 is composed of a refractory material formed by combining various oxides with carbon-containing raw materials such as graphite and organic resin, and is a substantially cylindrical body with a neck portion 6 having an enlarged diameter formed integrally thereon. Has been.

  In the nozzle body 2, a nozzle inner hole 3 through which molten steel flows is formed from the upper end of the nozzle body 2 to the lowermost part. The nozzle inner hole 3 communicates with the upper end opening 7 in the upper part, and communicates with the discharge ports 4a and 4b in the lower part.

  The discharge ports 4a and 4b are openings through which molten steel flows into the mold, and are provided opposite to the radial direction of the nozzle body 2 (at positions symmetrical with respect to the central axis of the nozzle body).

  The nozzle inner hole 3 is provided facing the upper part of the pair of discharge ports 4a and 4b (at a position symmetric with respect to the central axis of the nozzle body), and a pair of steps 5a and 5a continuous over the upper and lower sides of the meniscus A. 5b. By providing such steps 5a and 5b above and below the meniscus, molten steel in the vicinity of the meniscus is guided into the mold along the surface of the steps 5a and 5b that reduce the diameter of the nozzle inner hole 3 on the discharge port side. On the other hand, the flow rate of the molten steel is reduced compared with the case where the annular step is provided because the flow flows into the mold along the inner surface 3a of the nozzle inner hole 3 on the side opposite to the discharge port where the step is not provided. At the same time, since the steps 5a and 5b are provided at opposite positions (symmetric positions with respect to the central axis of the nozzle body), the discharge amount from the left and right discharge ports is also uniformed, and hot water caused by swells and the like An immersion nozzle for continuous casting with less surface fluctuation is configured. In particular, in the present invention, since the pair of steps 5a and 5b are continuously provided over the meniscus, the molten steel can be effectively guided to the center of the nozzle body 2 on the discharge port side. Can be further suppressed.

  Note that the upper and lower ends of the pair of steps 5a and 5b are preferably formed with tapered surfaces toward the inner hole surface of the nozzle inner hole 3, respectively, so that the steps with less melting and scattering of molten steel are obtained. Can be configured.

  The steps 5a and 5b are preferably formed within a range of 45 to 135 ° on the inner circumference of the nozzle inner hole 3, respectively. If the angle is less than 45 °, the step is too small to prevent the drift, and if it exceeds 135 °, it is too large to be the same as the annular step, so that the flow rate of the molten steel becomes too fast and the molten metal surface level changes frequently. Because it becomes. The steps 5a and 5b in this embodiment are provided over a range of 90 ° on the inner circumference of the nozzle inner hole 3.

  Moreover, it is preferable that each of the steps 5a and 5b is formed within a range of 5 to 15 mm in thickness. This is because if it is less than 5 mm, it is too low as a step to prevent drifting, and if it exceeds 15 mm, it is too high, the flow rate of the molten steel increases, and the molten metal surface fluctuations frequently occur. The steps 5a and 5b of this embodiment are each formed to a thickness of 10 mm.

  Furthermore, it is preferable that each of the steps 5a and 5b is formed within a range in which the length in the vertical direction is 80 to 250 mm. If it is less than 80, the step is too short to prevent drift, and if it exceeds 250 mm, it will be too long and the inner diameter will be the same, and the flow rate of the molten steel will become too fast, resulting in frequent fluctuations in the molten metal surface. Because it comes to do. The steps 5a and 5b in this embodiment are each formed with a vertical length of 170 mm.

  Furthermore, it is preferable that the lower ends of the steps 5a and 5b are separated from the upper ends of the discharge ports 4a and 4b by 100 mm or more. This is because when the length is less than 100 mm, the downward flow of the molten steel induced by the steps 5a and 5b directly affects the vicinity of the discharge port, thereby hindering good discharge.

  A pair of second steps 8a and 8b are formed on the upper portions of the pair of steps 5a and 5b of the nozzle inner hole 3 so as to be opposed to each other (at positions symmetrical with respect to the central axis of the nozzle body). In this embodiment, the second step provided above the steps 5a and 5b is not an annular step but is formed only on the discharge port side. Thereby, the flow velocity of molten steel is more relaxed.

  In addition, it is preferable that the upper and lower ends of the pair of second steps 8a and 8b are also formed in a tapered surface toward the inner hole surface of the nozzle inner hole 3, respectively, so that the melting damage and the scattering of the molten steel are further increased. A few steps can be configured.

  Each of the second steps 8a and 8b is preferably formed within a range of 45 to 135 ° on the inner periphery of the nozzle inner hole 3. If it is less than 45 °, the step is too small to prevent drift, and if it exceeds 135 °, it is too large to be the same as the annular step, and the flow rate of the molten steel becomes too fast, resulting in frequent fluctuations in the molten metal surface. Because it becomes like this. Note that the second steps 8a and 8b of this embodiment are provided over a range of 90 ° on the inner periphery of the nozzle inner hole 3, respectively.

  Moreover, it is preferable that the second steps 8a and 8b are each formed within a thickness range of 5 to 15 mm. This is because if it is less than 5 mm, it is too low as a step to prevent drifting, and if it exceeds 15 mm, it is too high, the flow rate of the molten steel increases, and the molten metal surface fluctuations frequently occur. The second steps 8a and 8b of this embodiment are each formed with a thickness of 10 mm.

  Furthermore, it is preferable that the second steps 8a and 8b each have a length in the vertical direction of 80 to 250 mm. If it is less than 80, it is because the step is too short to prevent the drift, and if it exceeds 250 mm, it is too long and the inner diameter is narrowed, and the flow rate of the molten steel is increased and the molten metal surface fluctuations frequently occur. Because it becomes. In addition, each of the steps 8a and 8b in this embodiment has a vertical length of 100 mm.

Next, another embodiment of the present invention shown in FIGS. 3 and 4 will be described.
The difference between the continuous casting immersion nozzle 10 and the continuous casting immersion nozzle 1 of this embodiment is as follows.
The only difference is that the second step 18 of the continuous casting immersion nozzle 10 is an annular step, and the others are the same as the continuous casting immersion nozzle 1. The same components as those of the continuous casting immersion nozzle 1 are denoted by the same reference numerals and description thereof is omitted.

  The second step 18 in this embodiment is an annular step formed with a thickness of 10 mm and a vertical length of 100 mm. Since the upper part of the drift of molten steel is larger, the flow rate of the molten steel is increased but the initial drift can be effectively suppressed by making the second step as an annular shape as in this embodiment. Thus, the case where the second step is an annular step is also included in the scope of the present invention.

(Water level fluctuation test)
The immersion nozzles N (n1, n2, n3, n4, n5, n6) for continuous casting of the following examples and comparative examples are depth (immersion) in a mold 50 having a mold size of 2000 × 200 mm as shown in FIG. The distance from the upper end of the discharge port of the continuous casting immersion nozzle N to the reference line L) was immersed for 200 mm, and the flow rate was 2.0 / min. Then, water was introduced from the upper end opening of the continuous casting immersion nozzle N (n1, n2, n3, n4, n5, n6) to observe the fluctuation of the molten metal surface. Specifically, the state of the molten metal surface is photographed and observed with the camera 60, and the maximum displacement (variation height) from the reference line L is measured to measure the continuous casting immersion nozzle N (n1, n2, n3). , N4, n5, n6) was quantified.

  As Example 1 (n1), the cylindrical body has a height of 1000 mm, an outer diameter of 130 mm, and an inner diameter of 80 mm, and a pair of discharge ports are provided at the lower opposing portions, and 100 mm above each discharge port upper end (step position). A continuous casting immersion nozzle was prepared by integrally forming a step having a length of 150 mm in the vertical direction (step length) and a thickness of 10 mm over 90 ° of the inner periphery. This continuous casting immersion nozzle n1 has partial steps provided continuously above and below the meniscus (reference line L in this test).

  As Example 2 (n2), in a cylindrical body having the same dimensions as in Example 1 and provided with a pair of discharge ports, the length in the vertical direction (step height) 150 mm above (upper step position) from the upper end of each discharge port. An immersion nozzle for continuous casting in which a step having a thickness of 150 mm and a thickness of 10 mm was integrally formed over 90 ° of the inner periphery was produced. The continuous casting immersion nozzle n2 also has partial steps provided continuously above and below the meniscus (the reference line L in this test).

  As Comparative Example 1 (n3), in a cylindrical body having the same dimensions as in Example 1 and provided with a pair of discharge ports, the vertical length (step length) is 150 mm, 100 mm above (step position) from the upper end of the discharge port, An immersion nozzle for continuous casting in which an annular step having a thickness of 10 mm was integrally formed was produced.

  As Comparative Example 2 (n4), an immersion nozzle for continuous casting was produced in which a step was not formed in a cylindrical body having the same dimensions as Example 1 and having a pair of discharge ports.

  As Comparative Example 3 (n5), as shown in FIG. 6, in a cylindrical body having the same dimensions as in Example 1 and having a pair of discharge ports 71, the vertical direction is 30 mm above the upper end of the discharge port 71 (step position). An immersion nozzle for continuous casting was prepared by integrally molding a step 72 having a length (step length) of 150 mm and a thickness of 10 mm over 90 ° of the inner periphery. This continuous casting immersion nozzle n5 has a step 72 below the meniscus (reference line L in this test).

  As Comparative Example 4 (n6), as shown in FIG. 6, in a cylindrical body having the same dimensions as in Example 1 and having a pair of discharge ports 71, the vertical direction is 250 mm above the upper end of the discharge port 71 (step position). An immersion nozzle for continuous casting was produced by integrally molding a step 73 having a length (step length) of 150 mm and a thickness of 10 mm over 90 ° of the inner periphery. This continuous casting immersion nozzle n6 has a step 73 above the meniscus (reference line L in this test).

  As a result of the molten metal surface fluctuation test, as shown in Table 1 below, the continuous casting immersion nozzles n3, n4, n5, and n6 of Comparative Examples 1 to 4 have much undulation or very much. In the continuous casting immersion nozzles n1 and n2 of Example 1 and Example 2, there was relatively little waviness. The fluctuation height was 30 to 35 mm in Comparative Examples 1 to 4, whereas it was as small as 25 mm in Example 1 and Example 2.

  Further, in the immersion nozzle n5 for continuous casting of Comparative Example 3 in which the step 72 is provided below the meniscus (the reference line L in this test), the flow velocity of the molten steel induced by the step 72 at the upper portion of the discharge port 71 is directly used as the discharge flow. Due to the influence, the fluctuation of the hot water level became large. Furthermore, the continuous casting immersion nozzle n6 of Comparative Example 4 in which the step 73 is provided above the meniscus (the reference line L in this test) is such that the molten steel guided to the center at the step 73 falls directly on the surface of the molten metal. Fluctuation has increased.

  From these results, it was confirmed that the continuous casting immersion nozzles n1 and n2 having partial steps provided continuously over the upper and lower sides of the meniscus are small and small in molten metal surface level.

DESCRIPTION OF SYMBOLS 1 Submerged nozzle for continuous casting 2 Nozzle body 3 Nozzle inner holes 4a, 4b Discharge ports 5a, 5b Step 6 Neck 7 Upper end openings 8a, 8b Second step

Claims (3)

A nozzle body;
A nozzle bore provided in the nozzle body for flowing molten steel;
A pair of discharge ports provided symmetrically facing the lower portion of the nozzle body,
The nozzle inner holes are provided symmetrically facing the upper portions of the pair of discharge ports, and have a pair of steps that are continuous within a range of 80 to 250 mm across the upper and lower sides of the meniscus, and a step on the side opposite to the discharge ports A continuous casting immersion nozzle characterized in that is not provided . 2. The continuous casting immersion nozzle according to claim 1, wherein a pair of second steps provided symmetrically opposite to each other are formed on top of the pair of steps in the nozzle inner hole.   2. The continuous casting immersion nozzle according to claim 1, wherein a second step formed in an annular shape is provided above the pair of steps in the nozzle inner hole.

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