JP2008221240A - Ladle for molten steel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ladle for molten steel which can reduce the generation of vortexes when discharging the molten steel and has sturdiness to load and thermal spalling to be subjected during receiving of the molten steel. <P>SOLUTION: The ladle for the molten steel having a discharge hole 5 for discharging the molten steel at the bottom is specified to 0.5 to 2D with respect to the smallest inner diameter D of the discharge hole in the shortest distance L from the central axis of the discharge hole 5 to an inner face 2a of the side wall. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a ladle for molten steel having a discharge hole for discharging molten steel at the bottom, and in particular, when discharging molten steel from the discharge hole, the molten steel is discharged while entraining slag floating due to the vortex of the molten steel. The present invention relates to a ladle for molten steel that has a structure that reduces the occurrence of heat.

  When the molten steel is discharged from the discharge hole at the bottom of the ladle for molten steel, especially in the latter half of the period, the molten steel becomes a vortex and is discharged from the ladle for molten steel. When this vortex occurs, the molten steel is discharged while entraining the slag floating on the upper surface of the molten steel, so that the slag is mixed into the discharged molten steel and the cleanliness is greatly impaired.

  As a method for reducing the mixing of slag into the molten steel and ensuring the cleanliness of the molten steel, there is a method in which casting is stopped and the remaining steel is processed when the remaining amount of the molten steel falls below a certain amount. There is a problem that a large yield loss occurs.

  On the other hand, in Patent Document 1, a baffle plate is arranged above a nozzle having a vertical axis, and the baffle plate isolates the nozzle from a flow directly downward from the surface of the liquid (molten steel). Such a flow control device is disclosed. In this flow control device, the partition is arranged so that the baffle plate is vertically separated from the nozzle, and this partition guides and controls the flow of the liquid, and the rotational flow around the axis line. Blocking and allowing liquid to flow radially under the baffle towards the axis before entering the nozzle.

  Further, in Patent Document 2, by providing a protruding wall (protrusion portion for preventing molten steel vortex generation) at a base portion constituting a well block for disposing a hot water discharge nozzle, the flow of molten steel in the vicinity of the hot water outlet is provided. There is disclosed a molten metal container that suppresses generation of molten steel vortex, prevents turbidity of molten steel due to entrainment in molten steel such as Noro, and prevents deterioration of the quality of metal products.

  However, in the structures of Patent Document 1 and Patent Document 2 described above, separate structures are provided around the discharge holes on the bottom surface of the container, and these structures are only supported by the bottom surface of the container. When subjected to a strong bending moment and thermal shock due to a molten steel flow, such as during steel, the strength may be insufficient and the steel may be destroyed.

  Moreover, in the structure of the said patent document 1 and the patent document 2, since the part which protruded upwards from the bottom face of a container is exposed to high temperature by molten steel and is overheated, hot strength falls and it wears out. In addition, there is a temperature difference between the portion exposed to the molten steel and the bottom of the container kept at a relatively low temperature, and thermal spalling is likely to occur.

Thus, the structures of Patent Document 1 and Patent Document 2 have poor durability and are not practical.
Japanese National Patent Publication No. 8-502209 JP 2000-218362 A

  The problem to be solved by the present invention is to provide a ladle for molten steel that can reduce the generation of vortices when discharging molten steel and that has high durability against loads and thermal spalling that are received during receiving steel. .

  When the discharge hole is in the vicinity of the center in the ladle for molten steel, the outer edge of the vortex generated along with the discharge of the molten steel can reach the inner surface of the side wall with the discharge hole as the center. On the other hand, when the discharge hole is near the side wall, the vortex is smaller and weaker than that centered on the discharge hole because the side wall is an obstacle. For this reason, it is thought that the amount of slag involved by the vortex decreases as the position of the discharge hole is closer to the side wall. Since the ladle for molten steel usually has an inner diameter of 2 to 4 m, generally around 3 m, the influence of the position of the discharge hole on the size of the vortex is considered to be extremely large.

  Therefore, as a result of investigating the relationship between the strength of the vortex and the position of the discharge hole by a water model experiment, the present inventor found that the closer the discharge hole is to the side wall, the weaker the vortex becomes. It has been found that when the shortest distance from the inner surface of the side wall of the pan is 0.5D or more and 2D or less with respect to the minimum inner diameter D of the discharge hole, the vortex is significantly reduced.

  That is, according to the present invention, in a ladle for molten steel provided with a discharge hole for discharging molten steel at the bottom, the shortest distance between the central axis of the discharge hole and the inner surface of the side wall is 0.5 D or more with respect to the minimum inner diameter D of the discharge hole. It is characterized by being 2D or less.

  With such a configuration, it is possible to reduce vortex generation when discharging molten steel, drastically reduce slag entrainment in molten steel, and to reduce vortex generation in Patent Document 1 and Patent Document 2 described above. Since such a special structure is not required, the durability of the ladle for molten steel is not lowered.

  On the other hand, due to equipment problems, the shortest distance between the central axis of the discharge hole and the inner surface of the side wall of the ladle for molten steel cannot be set to 0.5D or more and 2D or less with respect to the minimum inner diameter D of the discharge hole. There is. Specifically, the current ladle for molten steel is determined based on the mounting position of the sliding nozzle device, the work space for replacing the refractory of the sliding nozzle device, or the arrangement of the ladle for molten steel with respect to the tundish during continuous casting. If the discharge hole is provided near the side wall in FIG.

  In this case, the simulated wall is installed in close contact with the inner surface of the side wall of the ladle containing the tuyere brick of the molten steel ladle, and the shortest distance between the central axis of the discharge hole and the inner surface of the simulated wall is set to the minimum inner diameter D of the discharge hole. On the other hand, by setting it to 0.5D or more and 2D or less, the swirl of the molten steel can be reduced and the slag can be drastically reduced in the discharged molten steel. Here, the simulated wall is supported not only by the bottom surface of the ladle for molten steel but also by the inner surface of the side wall, and its shape can be simplified, so that it is resistant to strong bending moments and thermal shock caused by molten steel flow during receiving steel. It has sufficient durability, the deterioration of the durability of the ladle for molten steel is minimized, and the workability is also good.

  As described above, in the present invention, the discharge hole of the ladle for molten steel is disposed near the inner surface of the side wall (simulated wall), but the shortest distance between the central axis of the discharge hole and the inner surface of the side wall (simulated wall) is the minimum of the discharge hole. When the inner diameter D is less than 0.5D, a part of the discharge hole is covered with a side wall (simulated wall), and the discharge of the molten steel is hindered. Therefore, the lower limit of the shortest distance is set to 0.5D. The simulated wall inner surface refers to a surface on the discharge hole side of the side surfaces of the simulated wall.

  The upper limit of the shortest distance between the central axis of the discharge hole of the ladle for molten steel and the inner surface of the side wall (simulated wall) is 2D, and preferably 1.5D. When it becomes larger than 2D, the vortex becomes stronger and the amount of slag involved increases. In addition, D is preferably in the range of 40 mm or more and 120 mm or less from the minimum inner diameter of the discharge hole of a ladle for molten steel that is generally used.

  The discharge hole referred to in the present invention is a through hole provided for discharging molten steel to the bottom of a ladle for molten steel, and is usually a nozzle hole of an upper nozzle (also called a casting nozzle or a pouring nozzle). That is. A plate brick is often attached as a flow control means below the upper nozzle, but the nozzle hole of the plate brick is not said to be the discharge hole of the present invention. Further, although the inner diameter of the discharge hole of the upper nozzle may be reduced downstream, the minimum inner diameter D of the present invention is the portion with the smallest inner diameter of the reduced portion.

  Moreover, when installing a simulation wall in the bottom face of the ladle for molten steel, it is preferable that the height of a simulation wall shall be D-3D or less, and minimum width shall be 0.5D or more. When the height of the simulated wall is less than D, it does not function as a wall and vortex is likely to occur, and when it exceeds 3D, the effect does not change, but the volume of the simulated wall increases and the amount of received steel of the molten steel decreases, Loss occurs. On the other hand, when the minimum width is less than 0.5D, the strength becomes weak, which causes a problem. Here, the height of the simulated wall refers to the height to the substantial top of the simulated wall on the basis of the bottom surface of the ladle for molten steel.

  The simulated wall is not particularly limited as long as the simulated wall protrudes from the bottom surface of the ladle for molten steel and is in close contact with the bottom surface of the molten steel ladle and the inner surface of the side wall. Or a trapezoid or the like. In addition, the simulated wall can be formed simultaneously by pouring an indeterminate refractory when lining the refractory of the ladle for molten steel. Moreover, a block-shaped refractory can be manufactured and arrange | positioned through the mortar etc. as an adhesive agent between the bottom face and side wall of a ladle for molten steel.

  Further, the simulated wall is a simulated wall if the length of the close contact portion with the side wall is 1/50 or more and 1/2 or less, more preferably 1/36 or more and 1/3 or less of the inner peripheral length of the side wall. The supporting strength is sufficient. If the length of the close contact portion with the side wall is less than 1/50 of the inner peripheral length of the side wall, the strength is insufficient and the wall tends to collapse, and if it exceeds 1/2, the simulated wall becomes large and the volume of the ladle for molten steel Less.

  Furthermore, by providing a simulated wall, the discharge hole can be provided closer to the center of the bottom of the ladle for molten steel, so it is possible to secure a space for installing a molten steel flow control device such as a sliding nozzle device. The equipment can be used as it is.

  According to the ladle for molten steel of the present invention, it is possible to reduce the generation of vortices when discharging molten steel from the discharge hole, and to reduce the discharge of molten steel while entraining slag floating on the upper surface of the molten steel. And since it is not necessary to install a complicated structure in the ladle for molten steel, it is easy to construct and is excellent also in terms of durability.

  Embodiments of the present invention will be described below based on examples shown in the drawings.

  FIG. 1: shows the 1st Example of this invention, (a) is a top view which shows a part of bottom of the ladle for molten steel, (b) is AA sectional drawing in (a), (c). Is a BB cross section in (a).

  1 (a) and 1 (b), a refractory 2 is lined on the inner bottom and side walls of the iron shell 1. A tuyere brick 3 is embedded in the bottom of the ladle, an upper nozzle 4 is attached to the tuyere brick 3, and an inner hole of the upper nozzle 4 serves as a discharge hole 5 for molten steel. The upper nozzle 4 is mounted from the lower side of the ladle through a mortar so that the tuyere brick 3 is detachable. Although not shown in the figure, a sliding nozzle device for controlling the molten steel flow rate is attached below the upper nozzle 4.

  In the above configuration, the shortest distance L between the central axis of the discharge hole 5 and the side wall inner surface 2a shown in FIG. 1C is 0.5D or more and 2D or less (preferably 1.D) with respect to the minimum inner diameter D of the discharge hole 5. 5 or less).

  Thus, when the shortest distance L between the central axis of the discharge hole 5 and the side wall inner surface 2a is 0.5D or more and 2D or less (preferably 1.5 or less), the molten steel is discharged when the molten steel is discharged from the discharge hole 5. The effect of reducing the generation of vortices can be obtained.

  FIG. 2: shows the 2nd Example of this invention, (a) is a top view which shows a part of bottom of the ladle for molten steel, (b) is AA sectional drawing in (a), (c). Is a BB cross section in (a).

  Also in the second embodiment, the refractory 2 is lined as in the first embodiment, and the tuyere brick 3 and the upper nozzle 4 are mounted.

  Further, in the second embodiment, the simulated wall 6 is placed on the bottom surface 2 b in close contact with the side wall inner surface 2 a, and the inner surface 6 a on the discharge hole 5 side of the simulated wall 6 is located at the upper part of the inner wall of the tuyere brick 3. Yes. The simulated wall 6 is a precast block of an irregular refractory, and is joined to the bottom surface 2b and the side wall inner surface 2a by filling mortar. The shortest distance L between the inner surface 6a of the simulated wall 6 and the central axis of the discharge hole 5 is 0.5D or more and 2D or less (preferably 1.5D or less) with respect to the minimum inner diameter D of the discharge hole 5. ing. Further, as shown in FIG. 2A, the simulated wall 6 has a fan shape that tapers from the discharge hole 5 side toward the side wall inner surface 2a, and its minimum width W is the minimum inner diameter of the discharge hole 5. 0.5D or more with respect to D. Further, the length S of the contact portion with the side wall inner surface 2a is set to 1/36 or more and 1/3 or less with respect to the inner peripheral length of the side wall.

  Since the upper nozzle 4 for discharging molten steel is installed and replaced by inserting it from the bottom side of the ladle, if the simulated wall 6 is installed so as not to contact the upper nozzle 4 (so as not to interfere with it), the upper nozzle 4 is installed. Becomes easy.

  As in Example 2, the shortest distance L between the central axis of the discharge hole 5 and the simulated wall inner surface 6a is 0.5D or more and 2D or less (preferably 1.5D or less). The effect of reducing the vortex generation of the molten steel can be obtained when discharging the. Since the simulated wall 6 is in close contact with the side wall inner surface 2a, the simulated wall 6 can sufficiently withstand the impact and thermal shock caused by the molten steel flow at the time of receiving steel, and the heat is dissipated to the side wall, so that the hot strength is reduced due to overheating. Can be reduced, so that the durability is improved.

  FIG. 3: shows the 3rd Example of this invention, (a) is a top view which shows a part of bottom of the ladle for molten steel, (b) is AA sectional drawing in (a), (c). Is a BB cross section in (a).

  In this third embodiment, the simulated wall 6 is installed in the same manner as in the second embodiment. However, as shown in FIG. 3C, the inner surface 6a of the simulated wall 6 on the discharge hole 5 side is the discharge hole 6. Is located directly above the inner wall of the smallest inner diameter portion. That is, the shortest distance L between the central axis of the discharge hole 5 and the simulated wall inner surface 6a is 0.5D.

  Thus, the effect which reduces generation | occurrence | production of the vortex of molten steel more is acquired by making the simulation wall inner surface 6a approach to the discharge hole 5 to the maximum.

  In addition, in FIG.3 (c), although the simulation wall 6 is installed from the taper part upper part of the upper nozzle 4 for molten steel discharge to the extension line of the tuyere brick 3 upper part, this part may be a cavity.

  FIG. 4: shows the 4th Example of this invention, (a) is a top view which shows a part of bottom of the ladle for molten steel, (b) is AA sectional drawing in (a), (c). Is a BB cross section in (a).

  In the fourth embodiment, the simulated wall 6 is installed in the same manner as in the third embodiment. However, the simulated wall 6 of the fourth embodiment has no taper as shown in FIG.

  By making the simulated wall 6 into such a shape, the contact area between the simulated wall 6 and the side wall inner surface 2a, that is, the area supporting the simulated wall 6 is increased. The effect that durability improves is acquired.

  FIG. 5: shows the 5th Example of this invention, (a) is a top view which shows a part of bottom of the ladle for molten steel, (b) is AA sectional drawing in (a), (c). Is a BB cross section in (a).

  In the fifth embodiment, the simulated wall 6 is installed in the same manner as in the fourth embodiment. The simulated wall 6 of the fifth embodiment has an upper surface of the simulated wall 6 as shown in FIG. A taper is provided from the bottom to the bottom.

  By providing a taper on the upper surface of the simulated wall 6 in this manner, the volume of the ladle for molten steel can be increased as compared with the fourth embodiment, and the melting loss of the simulated wall 6 due to the molten steel flow is reduced. Further, with respect to the effect of reducing the generation of the vortex of the molten steel, since the height of the simulated wall 6 around the discharge hole 5 is important, the same effect as in Example 4 can be obtained.

  FIG. 6: shows the 6th Example of this invention, (a) is a top view which shows a part of bottom of the ladle for molten steel, (b) is AA sectional drawing in (a), (c). Is a BB cross section in (a).

  In this Example 6, the simulated wall 6 was installed in the same manner as in the previous Example 5, and the simulated wall 6 having a reduced shape as in Example 5 was installed to increase the volume of the ladle for molten steel. It is.

  This example shows the results of a water model experiment.

  FIG. 7 is a schematic diagram of a water model experimental apparatus. A discharge hole 5 having an inner diameter D of 20 mm was provided at the bottom of the container 7 having an inner diameter of 840 mm assuming a ladle for molten steel. The position of the discharge hole 5 is such that the shortest distance L between the central axis of the discharge hole 5 and the side wall inner surface 7a of the container is 420 mm (21D), 160 mm (8D), 60 mm (3D), 40 mm (2D), 26 mm (1. 3D) was set to 6 locations of 10 mm (0.5 D). Water was put into the container 7 so that the initial water level was 600 mm (mass is about 330 kg), and 3300 g of beads with a light specific gravity were put on the water surface and floated to make the mass ratio of water: beads about 100: 1.

  In the water model experiment, five of the six discharge holes 5 were closed, a swirling flow was previously applied to the water in the container 7, and then water was discharged from one discharge hole 5. As the water is discharged and the water level is lowered, the beads 8 on the water surface are entrained in the vortex and mixed with the water and discharged. The amount of the discharged beads 8 and the water level in the container 7 at that time were measured at each of the six discharge holes 5.

  In order to examine the effect of the simulated wall, a simulated wall 6 was installed as shown in FIG. The height H of the simulated wall 6 was 20 mm, and the width W was 40 mm. The shortest distance L1 between the central axis of the discharge hole 4 and the side wall inner surface 7a of the container is 60 mm (3D), and the shortest distance L2 between the central axis of the discharge hole 4 and the simulated wall inner surface 6a is 10 mm (0.5D). did. Also about what installed this simulation wall 6, the quantity of the bead 8 and the water level in the container 7 at that time were measured similarly to said measuring method.

  FIG. 9 shows the results of the water model experiment. The amount of beads discharged was expressed as the weight of beads discharged up to each water level / the total weight of beads placed in a container. For example, in the case of L = 21D, about 24% of the beads that are initially placed when the water level reaches 200 mm are discharged, and further about 96% of the beads are discharged when the water level reaches 100 mm. .

  When the shortest distance L from the side wall inner surface 7a of the container to the central axis of the discharge hole 5 is 420 mm (21D), that is, when the discharge hole 5 is provided at the center of the container 7, a vortex is generated in the container from the initial stage and the beads It can be seen that water is discharged while entraining. The bead discharge amount decreases as the shortest distance L from the inner wall of the container to the central axis of the discharge hole decreases. When the shortest distance L is 10 mm (0.5 D), the bead discharge amount is the largest. Is decreasing. In addition, when L = 8D, about 82% of beads are discharged when the water level reaches 20 mm, but when L = 2D, about 24%, and when L = 1.3D, about 13%. It can be seen that there is a significant decrease. The generated vortices are also very small. That is, in the ladle for molten steel, it can be seen that the discharge amount of slag is drastically reduced by setting the position of the discharge hole to L = 2D or less, preferably L = 1.3D or less. In addition, it is proved from many past experimental reports that the correlation between this water model experiment and the actual behavior in molten steel is high.

  In addition, when the simulated wall is installed as shown in FIG. 8, the bead discharge amount is smaller than when there is no simulated wall (the shortest distance L = 60 mm (3D)), and moreover, it is very different from the case of L = 0.5D. It is close to the value, and the effect of suppressing vortices by installing a simulated wall appears.

  Further, FIG. 10 shows the relationship between the ratio of beads discharged until the water level reaches 20 mm and the shortest distance L. From FIG. 10, it can be seen that when L is changed from 3D to 2D, the amount of discharged beads decreases greatly, and when L becomes 1.3D, the amount of discharged beads decreases.

The 1st Example of this invention is shown, (a) is a top view which shows a part of bottom of the ladle for molten steel, (b) is AA sectional drawing in (a), (c) is (a). It is a BB cross section in. The 2nd Example of this invention is shown, (a) is a top view which shows a part of bottom of the ladle for molten steel, (b) is AA sectional drawing in (a), (c) is (a). It is a BB cross section in. The 3rd Example of this invention is shown, (a) is a top view which shows a part of bottom of the ladle for molten steel, (b) is AA sectional drawing in (a), (c) is (a). It is a BB cross section in. The 4th Example of this invention is shown, (a) is a top view which shows a part of bottom of the ladle for molten steel, (b) is AA sectional drawing in (a), (c) is (a). It is a BB cross section in. The 5th Example of this invention is shown, (a) is a top view which shows a part of bottom of the ladle for molten steel, (b) is AA sectional drawing in (a), (c) is (a). It is a BB cross section in. The 6th Example of this invention is shown, (a) is a top view which shows a part of bottom of the ladle for molten steel, (b) is AA sectional drawing in (a), (c) is (a). It is a BB cross section in. It is a schematic diagram of a water model experimental apparatus. It is a schematic diagram of a water model experimental apparatus with a simulated wall, (a) is a cross-sectional view, and (b) is a plan view. The water model experiment results are shown. The relationship between the shortest distance L from the inner wall of the container in the water model experiment to the central axis of the discharge hole and the bead discharge amount is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Iron skin 2 Refractory 2a Side wall inner surface 2b Bottom surface 3 Feather brick 4 Upper nozzle 5 Discharge hole 6 Simulated wall 6a Simulated wall inner surface 7 Container 7a Side wall inner surface 8 Bead

Claims (3)

  In a ladle for molten steel having a discharge hole for discharging molten steel at the bottom, the shortest distance between the central axis of the discharge hole and the inner surface of the side wall is 0.5D or more and 2D or less with respect to the minimum inner diameter D of the discharge hole. A ladle for molten steel.   In a ladle with a discharge hole for discharging molten steel at the bottom, the simulated wall is placed on the bottom surface in close contact with the inner surface of the side wall, and the shortest distance between the central axis of the discharge hole and the inner surface of the simulated wall is the minimum of the discharge hole. A ladle for molten steel, wherein the ladle has an inner diameter D of 0.5D to 2D.   The ladle for molten steel according to claim 2, wherein the height of the simulated wall is not less than D and not more than 3D, and the minimum width is not less than 0.5D.

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