JP2007301588A - Ladle for continuous casting - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ladle for continuous casting, wherein the contaminated material in molten metal can economically be reduced. <P>SOLUTION: This ladle is provided with: an almost columnar refractory board 12 disposed at a vertical molten metal flowing passage in an upper nozzle 3; a projected ring 13 inserted between the outer peripheral lower end part of the refractory board 12 and the inner wall surface of a lower part plate 3b; and refractory particles 14 to be filled into a ring-like space 11 between the outer peripheral surface of the refractory board 12 formed on the projected ring 13 and the inner wall surfaces of an upper part plate 3a and the lower part plate 3b. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a ladle for continuous casting, and more particularly, in continuous casting of molten metal mainly composed of molten steel, continuous casting that can suppress the contamination of the molten metal when pouring the molten metal in the ladle into the tundish. Related to ladle.

  Since the present invention constitutes a part of a so-called continuous casting facility, the outline of the continuous casting facility will be briefly described first.

  As shown in FIG. 5, the continuous casting equipment includes a ladle 21 that receives a molten metal of a converter (not shown), a tundish 23 that receives the molten metal in the ladle 21 through an injection pipe 22, and a tundish. 23, a mold 25 for receiving the molten metal in the slab 24 through the immersion nozzle 24, a spray nozzle 26 for spraying cooling water over the entire width of the slab, and electromagnetic induction stirring of the molten metal in the slab to increase equiaxed resinous crystals, Mainly composed of an electromagnetic induction stirrer 27 that disperses segregation of the solute element at the final solidification position among a number of equiaxed crystals, a number of support roll groups 28, a slab-drawing dummy bar 29, and a gas cutter 30. Is done.

  When transferring the molten metal from the ladle 21 to the tundish 23 and from the tundish 23 to the mold 25, the refractory injection tube 22 and the immersion nozzle 24 are used to block the oxidation caused by the contact between the molten metal and the air. The dish 23 is provided with a weir and a baffle in order to avoid the slag from getting caught in the molten metal, and the floating separation of the nonmetallic inclusions is achieved. In addition, for the purpose of suppressing the fluctuation of the molten metal surface and improving the surface properties of the solidified shell, an apparatus for applying a magnetic field to the mold 25 to control the flow of the molten metal flowing from the tundish 23 is used. A vibration device is installed to prevent seizing of the slab, and the support roll group 28 increases rigidity and decreases the interval between the rolls to prevent slab bulging due to the molten metal static pressure and the resulting cracking and segregation. Various measures are taken to improve the quality of the slab.

  However, nevertheless, when pouring the molten metal from the ladle 21 to the tundish 23, the metal melt is re-oxidized in the tundish due to several factors, and the cleanliness of the molten metal is lowered. There are two main causes of the decrease in cleanliness, the first being oxidation from an atmosphere containing air, and the second being oxidation by slag containing oxide. Of these, oxidation from the atmosphere can be almost completely prevented by various measures.

  On the other hand, as a method for preventing oxidation of the molten metal by slag, for example, Patent Document 1 discloses a slag intrusion prevention container including a cylindrical side wall portion, a conical roof portion on the upper side, and a flat bottom portion. A method for preventing slag intrusion by suspending from the ladle so that the center of the inlet of the molten metal from the ladle to the tundish coincides with the center of the container is disclosed. The method using a container for preventing intrusion has a problem in operability such as complicated handling of the container, and it cannot be said that the effect of preventing the infiltration of slag is sufficient.

  Furthermore, the invention described in Patent Document 1 does not mention the contamination of the molten metal caused by the refractory particles filled in the upper nozzle of the ladle described below. That is, as a matter which has not been paid attention to the contamination of the molten metal in the continuous casting method, there can be mentioned problems associated with refractory particles filled in the upper nozzle of the ladle described below.

That is, since continuous casting is performed by alternately injecting molten metal into the tundish from two or more ladles that store molten metal supplied from the converter, the molten metal is injected into the tundish. It is necessary to seal the molten metal discharge port at the bottom of the ladle, and as shown in FIG. 6, the upper nozzle is a molten metal discharge port provided at the bottom of the ladle that does not discharge the molten metal (see reference numeral 21 in FIG. 5). 31 is sealed by a flange portion 33 of a sliding nozzle 32 that slides along the bottom surface of the ladle, and refractory particles 34 (100 for preventing the molten metal from entering and solidifying the molten metal flow path in the upper nozzle 31. Refractory particles mainly composed of silica or chromium having a mesh size, about 40 to 60 kg / charge). However, the refractory particles flow into the tundish together with the molten metal in the ladle at the time of pouring and finally become a product defect as non-metallic inclusions when solidified. As measures to prevent this, the initial molten metal flowing into the tundish from the ladle is discarded, or the slab in the range that seems to contain the refractory particles is treated as an out-of-class product. Yes. However, such a method causes a significant decrease in yield. Some refractory particles float on the surface of the molten metal due to the specific gravity of the weirs provided in the tundish, but a considerable amount of refractory particles are mixed in the molten metal and become non-metallic inclusions during solidification. As a result, the quality of the cast product is reduced.
Japanese Patent Laid-Open No. 7-185753

  The present invention has been made in view of such problems of the prior art, and its purpose is to provide refractory particles filled in the upper nozzle of the ladle and slag flowing into the ladle from the converter. An object of the present invention is to provide a ladle for continuous casting that can economically reduce contaminants in molten metal caused by the above.

  In order to achieve the above object, the present invention provides a ladle for continuous casting in which a molten metal in a ladle is discharged from an upper nozzle provided at the bottom of the ladle through a sliding nozzle. A substantially cylindrical fireproof board to be disposed on, a tension ring fitted between the lower end of the outer periphery of the fireproof board and the inner wall surface of the upper nozzle, and an outer surface of the fireproof board formed on the tension ring and the upper nozzle. It has refractory particles filling a ring-shaped space between the wall surfaces.

  According to such a configuration, the refractory board having a certain size disposed in the molten metal flow path does not enter the molten metal and floats on the molten metal surface, thereby reducing contaminants (refractory particles) contained in the molten metal. be able to.

  In the above configuration, a steel support member for supporting the fireproof board from below is arranged at the lower part of the molten metal flow path in the upper nozzle, one end of the support member is supported by the flange of the sliding nozzle, and the other end of the support member is It is preferable to press fit into the fireproof board.

  If it does so, the filling amount itself of a refractory particle can be decreased, and the contaminant contained in a molten metal can be reduced further.

  Furthermore, if the fireproof board is tapered so that the outer diameter decreases from the bottom of the ladle toward the inside of the ladle, a strong downward pressure is exerted by the molten metal's static pressure when pouring the molten metal from the ladle into the tundish. Thus, the fireproof board released from the restraint by the tension ring flows down integrally with the molten metal flow, and a smooth hot water flow from the upper nozzle through the sliding nozzle into the tundish can be secured.

  In addition, the slag that flows out from the converter when steel is levitated above the molten metal in the ladle, but when the amount of molten metal in the ladle decreases and the end of pouring into the tundish is reached, A vortex is generated in the vicinity of the nozzle, and the slag is likely to be mixed into the molten metal, which becomes a non-metallic inclusion and causes the quality of the cast product to deteriorate.

  Therefore, if a gas injection hole for injecting inert gas toward the molten metal in the ladle is provided at the upper end of the upper nozzle, the inert gas is ejected from the gas injection hole toward the molten metal in the ladle. Thus, slag having a low specific gravity can be caused to accompany the inert gas and float on the surface of the molten metal, thereby reducing non-metallic inclusions mixed in the cast product.

  In addition, if gas ejection holes are provided at equal intervals in the circumferential direction of the upper end of the upper nozzle, the inert gas is ejected from the gas ejection holes toward the molten metal in the ladle so that it is evenly distributed in the molten metal. It can be expected that the slag entrainment effect on the molten metal is further enhanced by the slag levitation action caused by the inert gas flow existing in the molten metal.

  Contaminants contained in the molten metal can be economically reduced and the quality of the cast product can be improved by a simple means of arranging a substantially cylindrical fireproof board in the molten metal flow path in the upper nozzle of the ladle. .

Embodiments of the present invention will be described below with reference to the drawings. However, the present invention is not limited to the following embodiments, and can be appropriately changed or modified without departing from the technical scope of the present invention. .
(Continuous casting equipment)
FIG. 1 is a schematic cross-sectional view of an example of continuous casting equipment to which a ladle according to the present invention is applied. In FIG. 1, a ladle 1 accommodates a molten metal 2, an upper nozzle 3 is formed at the bottom of the ladle 1, and a sliding nozzle that slides along the bottom surface of the ladle 1 below the upper nozzle 3. 4 is installed, and an injection tube 5 is attached to the sliding nozzle 4 in a fixed manner. Therefore, the sliding nozzle 4 and the injection tube 5 can be integrally slid in the direction of both arrows by a driving device (not shown). Moreover, the injection tube 5 is immersed in the molten metal 2 in the tundish 6 provided below the ladle 1. The sliding nozzle 4 is a means for adjusting the flow rate of the molten metal 2 discharged from the ladle 1, and the sliding nozzle 4 integrated with the injection pipe 5 slides along the bottom surface of the ladle 1 in the direction indicated by the double arrow. If the upper nozzle 3 is fully closed and the supply of the molten metal 2 is cut off, or if the opening of the upper nozzle 3 and the opening of the sliding nozzle 4 coincide, that is, if the opening is fully opened, a predetermined amount The molten metal 2 is discharged toward the tundish 6. A plurality of weirs 7 are installed in the tundish 6, and the bottom part on the opposite side in the longitudinal direction with respect to the installation position of the injection pipe 5 with respect to the tundish 6 is an immersion that serves as a flow path for supplying molten metal to the mold 9. A nozzle 8 is installed, and a slab 10 is manufactured through a mold 9.

  Thus, the opening of the upper nozzle 3 and the opening of the sliding nozzle 4 are aligned and the molten metal 2 in the ladle 1 is tundished while the tip of the injection tube 5 is immersed in the molten metal 2 in the tundish 6. 6 is injected. The molten metal 2 in the tundish 6 is blocked from coming into contact with a weir 7 provided at an appropriate position, and a part of lightweight impurities such as refractory particles contained in the molten metal 2 along the weir 7. However, there is a considerable amount of refractory particles that are mixed in the molten metal 2. In this way, the molten metal 2 accompanied with the refractory particles is cooled and solidified in the mold 9 through the immersion nozzle 8 to produce a slab 10 containing inclusions.

Although the above has described single strand casting for the sake of simplicity, in general, multi-strand casting in which molten metal is alternately poured into a tundish from a plurality of ladles is performed. In this case, the molten metal outlet of the ladle from which the molten metal is not discharged needs to be closed, and for this reason, the upper nozzle 3 of the ladle 1 shown in FIG. 1 is filled with refractory particles. However, the refractory particles flow into the tundish 6 together with the molten metal 2 at the initial stage of injection and cause the molten metal to be contaminated.
(Upper nozzle)
Therefore, in order to prevent the contamination of the molten metal or suppress the contamination of the molten metal, the present inventor employs an upper nozzle having a configuration as shown in FIGS. FIG. 2 is an enlarged sectional view of an embodiment of the upper nozzle of the ladle of the present invention, and FIG. 3 is an enlarged sectional view of another embodiment of the upper nozzle of the ladle of the present invention.

In FIG. 2, the upper nozzle 3 is composed of an upper plate 3a and a lower plate 3b. In the upper and lower molten metal flow path in the center of the upper nozzle 3, a taper-shaped substantially circle whose outer diameter gradually decreases from the ladle bottom side (lower side in FIG. 2) toward the inside of the ladle (upper side in FIG. 2). A column-shaped fireproof board 12 is disposed, and a stretchable refractory stretch ring 13 is inserted between the lower end of the outer periphery of the fireproof board 12 and the inner wall surface of the lower plate 3 b, and is formed on the stretch ring 13. In the ring-shaped space 11 between the outer peripheral surface of the refractory board 12 and the inner wall surfaces of the upper plate 3a and the lower plate 3b, refractory particles 14 (with a particle size in the range of about 590 to 1190 μm, Cr ₂ O ₃ and SiO _{2 2} and refractory particles containing 70% by weight or more of the total of the three components of Fe ₂ O ₃ . Since the outer diameter of the tension ring 13 is slightly larger than the inner diameter of the lower plate 3 b and the inner diameter of the tension ring 13 is slightly smaller than the outer diameter of the fireproof board 12, Can be pressed and held. Reference numeral 18 denotes a sliding nozzle flange. The fireproof board 12 is obtained by drying at about 200 ° C. what is formed by kneading about 90% by weight of MgO, clay, and phenol resin (binder). As a material of the fireproof board, any material other than the above, for example, brick or ceramic can be used as long as it has fire resistance. Further, in the present invention, the fireproof board includes a fired refractory, a molded product of refractory castable, a molded product of refractory fiber, and the like.

  Three gas injection holes 15 for injecting an inert gas obliquely upward toward the molten metal in the ladle 1 are provided in the upper end portion of the upper plate 3a at three positions facing each other. The gas ejection hole 15 is connected to an Ar gas supply source (not shown). In FIG. 2, only three gas ejection holes 15 are shown at positions opposed to each other by 180 °. However, if necessary, three or more locations at substantially equal intervals in the circumferential direction of the upper end portion of the upper plate 3a. A plurality of inert gas ejection holes can be provided at each location.

  In FIG. 3, which is an embodiment different from FIG. 2, a substantially cylindrical refractory board 16 is installed in the upper part of the molten metal flow path in the upper nozzle 3. In the lower part of the molten metal flow path in the upper nozzle 3, a pipe-like support member made of mild steel is used to support the substantially cylindrical fireproof board 16 (kneaded, molded and dried with the same material as the fireproof board 12) from below. 17, one end of the pipe-like support member 17 is supported by the flange 18 of the sliding nozzle, and the other end of the pipe-like support member 17 is reduced in diameter and press-fitted into the fireproof board 16. Also in this case, as in FIG. 2, the substantially cylindrical fireproof board 16 has a taper whose outer diameter gradually decreases from the bottom of the ladle (downward in FIG. 3) toward the inside of the ladle (upward in FIG. 3). The stretch ring 19 made of a stretchable refractory that is shaped and fitted between the lower end of the outer periphery of the fireproof board 16 and the inner wall surface of the upper plate 3a can exert a stretching effect in the radial direction. It has an outer diameter slightly larger than the inner diameter of the upper plate 3 a and an inner diameter slightly smaller than the outer diameter of the fireproof board 16. The ring-shaped space 11 between the outer peripheral surface of the refractory board 16 formed on the tension ring 19 and the inner wall surface of the upper plate 3 a is filled with refractory particles 14.

  Note that a material made of mild steel can be adopted as the material of the tension ring 13 or 19. In this case, the installation to the fireproof board is somewhat troublesome as compared with the one made of the stretchable refractory, but in FIG. 2 or 3, the fireproof board 12 or 16 is directed from the ladle bottom side toward the inside of the ladle. Since the outer diameter gradually decreases in taper shape, the sliding nozzle flange 18 is slid to open the lower end of the molten metal flow path of the upper nozzle 3, and the brazing ring 13 or 19 made of mild steel is connected to the diameter of the refractory board 12 or 16. It is attached to the small portion and inserted into the molten metal flow path of the upper nozzle 3, and the locking member locked to the tensile ring 13 or 19 made of mild steel is pulled from the opening at the lower end of the molten metal flow path to pull the tensile ring 13 made of mild steel or By pulling down 19 along the tapered surface of the refractory board 12 or 16, as shown in FIG. It can be mounted between the lower plate 3b and the inner wall surface of the lower plate 3b, or as shown in FIG. 3, a soft steel tension ring 19 can be mounted between the lower end of the outer periphery of the refractory board 16 and the inner wall surface of the upper plate 3a. it can.

  As shown in FIG. 4, the gas ejection holes provided in the upper plate 3a are configured such that convex portions 20a and concave portions 20b are alternately formed at the upper end portion of the upper plate 3a, and the gas ejection holes 15 are provided in the convex portions 20a. Can be adopted. If it does in this way, since the recessed part 20b becomes a runway of a molten metal, it can be expected that the flow of the molten metal becomes smooth by increasing the cross-section of the flow path when discharging the molten metal from the ladle 1.

  According to the ladle for continuous casting of the present invention configured as described above, in FIG. 1, the molten metal 2 is injected from the ladle 1 into the tundish 6 through the upper nozzle 3, the sliding nozzle 4 and the injection pipe 5. 2 when the structure of the upper nozzle 3 is adopted, when the substantially columnar refractory board 12, the refractory particles 14 and the tension ring 13 flow into the tundish 6 along with the molten metal, Although the object particles 14 are mixed in the molten metal 2, the stretchable refractory stretch ring 13 and the substantially cylindrical refractory board 12 are not mixed in the molten metal and float on the surface of the molten metal 2 in the tundish 6. To do. Therefore, contamination of the molten metal due to non-metallic inclusions can be reduced. In addition, when the thing made from a mild steel is employ | adopted as the tension ring 13, the tension ring made from mild steel melt | dissolves in a molten metal rapidly.

  When the structure of FIG. 3 is adopted as the structure of the upper nozzle 3, the filling amount of the refractory particles 14 is considerably smaller than that of FIG. 2, so in FIG. 1, the ladle 1 to the upper nozzle 3, the sliding nozzle 4 and When the molten metal 2 is injected into the tundish 6 through the injection pipe 5, the amount of non-metallic inclusions mixed in the molten metal 2 can be greatly reduced. It can be expected to improve dramatically compared to that of FIG.

  Further, in FIG. 1, when pouring the molten metal from the ladle 1 into the tundish 6, the gas jet hole 15 of the upper plate 3 a of the upper nozzle 3 shown in FIG. 2 or 3 is directed toward the molten metal 2 in the ladle 1. By ejecting the inert gas obliquely upward, the low specific gravity slag is caused to accompany the inert gas and float on the surface of the molten metal, thereby reducing non-metallic inclusions mixed in the cast product. The amount of the inert gas may be a constant amount from the beginning to the end of discharging the molten metal 2 from the ladle 1, but at the end of the molten metal injection, a vortex is generated near the upper nozzle 3 and slag is mixed into the molten metal. Considering the fact that it becomes easier, it is economical to gradually increase the amount of metal spray from the time when the amount of molten metal in the ladle is reduced to about 1/5 to the end of the ladle, thereby suppressing the inclusion of slag in the molten metal This is also very effective. For example, the gas amount is preferably about 5 to 10 times at the end of the initial gas ejection amount. Moreover, when the thing shown in FIG. 4 is employ | adopted as the gas ejection hole 15 provided in the upper end part of the upper plate 3a, since the recessed part 20a becomes a runway of a molten metal, when discharging a molten metal from the ladle 1 It can be expected that the hot water flow becomes smooth as the cross section of the flow path increases.

  2 and 3, the larger the volume of the refractory board 12 or 16, the smaller the filling amount of the refractory particles 14, so that the quality of the cast product can be greatly improved. .

  In addition, in a continuous casting facility that manufactures a product (for example, stainless steel) that is extremely disliked from inclusion of non-metallic inclusions in the product, as the refractory particles filled in the upper nozzle 3 of the ladle 1 shown in FIG. Nail waste (granular waste generated when nails are processed) is used. However, in this case, the molten metal in the ladle 1 and the nail scraps are fused to generate a so-called shelf hanging phenomenon, and the molten metal is not discharged only by sliding the sliding nozzle 4 to the fully open state. Then, complicated operation of ensuring a runner by spraying oxygen gas toward nail waste and dissolving nail waste in red heat is performed.

  INDUSTRIAL APPLICABILITY The present invention can be applied to a ladle for continuous casting used when continuously casting a molten metal mainly composed of molten steel, and in particular, a molten metal when pouring a molten metal in a ladle into a tundish. It is suitable as a ladle for continuous casting that can suppress contamination of the steel.

It is a schematic sectional drawing of an example of the continuous casting installation to which the ladle of this invention is applied. It is an expanded sectional view of one embodiment of the upper nozzle of the ladle of the present invention. It is an expanded sectional view of another embodiment of the upper nozzle of the ladle of this invention. It is a perspective view which expands and shows the upper end part of another embodiment of the upper nozzle of the ladle of this invention. It is the schematic of a general continuous casting installation. It is an expanded sectional view near the upper nozzle of the conventional ladle.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ladle 2 Molten metal 3 Upper nozzle 3a Upper plate 3b Lower plate 4 Sliding nozzle 5 Injection pipe 6 Tundish 7 Weir 8 Immersion nozzle 9 Mold 10 Slab 11 Ring-shaped space 12 Refractory board 13 Strut ring 14 Refractory particle 15 Gas Ejection hole 16 Fireproof board 17 Pipe-shaped support member 18 Flange of sliding nozzle 19 Strut ring 21 Ladle 22 Injection pipe 23 Tundish 24 Immersion nozzle 25 Mold 26 Spray nozzle 27 Electromagnetic induction stirrer 28 Support roll group 29 Dummy bar 30 Gas cutting machine

Claims (5)

  In the ladle for continuous casting that discharges the molten metal in the ladle from the upper nozzle provided at the bottom of the ladle through the sliding nozzle, the upper nozzle is a substantially cylindrical refractory board disposed in the vertical melt flow path, A strut ring inserted between the lower end of the outer periphery of the fireproof board and the inner wall surface of the upper nozzle, and a ring-shaped space between the outer peripheral surface of the fireproof board formed on the strut ring and the inner wall surface of the upper nozzle is filled. A ladle for continuous casting, comprising refractory particles.   A steel support member for supporting the fireproof board from below is arranged at the bottom of the molten metal flow path in the upper nozzle, one end of the support member is supported by the flange of the sliding nozzle, and the other end of the support member is placed in the fireproof board. The ladle for continuous casting according to claim 1, wherein the ladle is press-fitted.   The ladle for continuous casting according to claim 1 or 2, wherein the refractory board has a tapered shape in which the outer diameter decreases from the ladle bottom side toward the inside of the ladle.   The ladle for continuous casting according to claim 1, 2 or 3, wherein a gas ejection hole for ejecting an inert gas toward the molten metal in the ladle is provided at the upper end of the upper nozzle.   The ladle for continuous casting according to claim 4, wherein the gas ejection holes are provided at equal intervals in the circumferential direction of the upper end portion of the upper nozzle.

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