JP2008062288A - Method and structure for sealing nozzle joint part in continuous casting facility for steel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and structure for sealing a nozzle joint part in a continuous casting facility for steel capable of preventing air from involving in a nozzle. <P>SOLUTION: In the sealing method of the nozzle joint part in the continuous casting facility for steel, the nozzle joint part is sealed with nonmetallic melt material to prevent air from being included in the nozzle. In the sealing structure of the nozzle joint part in the continuous casting facility for steel, a nonmetallic melt material 10 for preventing air from being included in the nozzle is held between packing material 9 made of unshaped refractories or flame retardant material and the nozzle joint surface to be joined. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a sealing method and a sealing structure of a nozzle joint in a steel continuous casting facility capable of preventing air from being caught in a nozzle.

Conventionally, in continuous casting of steel, molten steel is continuously supplied into a mold by joining a ladle nozzle and a long nozzle, and a tundish lower nozzle and an immersion nozzle, respectively. This joint surface is usually joined using an irregular refractory or a flame retardant material packing material, but since it is a solid-to-solid joint, there is a minute gap and complete airtightness. It could not be retained. In addition, because the molten steel flows inside the nozzle at high speed, due to the aspirator principle, air is entrained from the joint, resulting in product defects due to air bubbles entering the product and alumina clusters generated by air oxidation. There was also a problem that problems such as product defects and nozzle clogging occurred.
On the other hand, in order to prevent the entrainment of air, a method of supplying an inert gas such as argon gas to the joint is also being studied. In this case, however, there is no entrainment of oxygen and the problem of alumina clusters can be prevented. There was a problem of causing defects in Ar bubbles inside.

  In order to solve the above problem, various techniques for improving the airtightness of the nozzle joint have been developed. For example, the high corrosion resistance and airtight packing material disclosed in Patent Document 1 includes a low melting point metal contained in a refractory powder, thereby fixing oxygen mixed from outside air as an oxide and preventing defects due to oxygen mixing. is doing. However, since the fixed oxygen generates an oxide film on the metal surface, there is a problem that the oxidation reaction rate is lowered and the oxygen absorption ability is lowered.

On the other hand, in the invention disclosed in Patent Document 2, the packing material contains a metal having a high binding force with oxygen and a vapor pressure of 1 atm or higher at the use temperature. In this invention, since the metal vapor is continuously supplied, the stagnation of the reaction for fixing oxygen does not occur.
In either case, however, oxygen cannot be completely absorbed by the inhalation of the atmosphere only by containing metal as part of the packing material, and the packing material and the nozzle interface are in solid contact. However, it was impossible to completely prevent the air from being sucked through the fine gaps between the solids.

Furthermore, in the invention disclosed in Patent Document 3, the adhesion of the nozzle joint surface is improved by using a packing material that is softened at the operating temperature. However, in normal continuous casting of steel, the nozzle is replaced during casting, but a part of the softened packing material tends to remain on the joint surface of the tundish lower nozzle or immersion nozzle, so it was installed next. There was a problem that the adhesion of the nozzle packing material was hindered and the sealing degree was lowered.
Japanese Patent Publication No. 60-15592 JP 2001-105107 A Japanese Patent Laid-Open No. 2003-25060

  The present invention solves the problems as described above, stably seals the nozzle joint surface for a long time, and prevents the product defects and operational troubles caused by air suction. The present invention has been completed for the purpose of providing a sealing method for a part and a sealing structure.

  The present invention made in order to solve the above problems is a method for sealing a nozzle joint in a steel continuous casting facility, wherein the nozzle joint is sealed with a non-metallic melt to entrain air into the nozzle. According to a first aspect of the present invention, there is provided a sealing method for a nozzle joint in a continuous casting equipment for steel, which is characterized by the prevention. A nozzle in a continuous casting equipment for steel, characterized in that a non-metallic melt that prevents air from being entrained in the nozzle is held between a packing material made of a flammable material and a nozzle joining surface to be joined. The seal structure of the joint portion is the second invention.

  In the present invention, the nozzle joint is sealed with a non-metallic melt, so that the fine gap generated by the joining of the solids is completely filled, and the suction of air is surely prevented. Further, since the non-metallic melt is used, the sealing degree of the joint portion of the nozzle mounted next after remaining on the joint surface at the time of nozzle replacement is not reduced. Therefore, it is possible to prevent product defects and operational troubles due to air suction, and as a result, it is possible to contribute to the improvement of the productivity and quality of steel. Moreover, since it can be operated without the addition of new equipment, the economic effect is great.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic diagram of a ladle, a long nozzle, a tundish, and an immersion nozzle used for continuous casting of steel.
In FIG. 1, 1 is a ladle, 2 is a sliding nozzle upper plate, 3 is a sliding nozzle middle plate, 4 is a sliding nozzle lower plate, 5 is a long nozzle, 6 is a tundish, 7 is an immersion nozzle, and 8 is a mold. . Reference numeral 9 denotes a packing material made of an indeterminate refractory or a flame retardant material that is attached to the joint of the nozzle.

  The present invention is characterized in that, as a method for sealing a nozzle joint in a steel continuous casting facility, the nozzle joint is sealed with a non-metallic melt to prevent air from being caught in the nozzle.

As a result of various studies on methods for improving the sealing performance of the nozzle joint, the present inventor has found that a method for sealing the nozzle joint with a non-metallic melt is optimal, and has completed the present invention.
That is, by using a non-metallic melt, it is possible to completely seal the minute gaps at the joints between the solids, and there is no reaction with the refractory that constitutes the nozzle, so the sealing performance is maintained for a long time. It can be maintained. On the other hand, in the continuous casting of steel, the temperature of the nozzle changes from 700 ° C. to 1600 ° C. depending on the part. However, if it is a non-metallic melt, the non-metal used can be changed depending on the position of the sealing material. Good. For example, when the temperature of the seal portion is 1200 ° C., a nonmetal having a melting point of 1100 ° C. may be used.
Examples of the nonmetal include oxides such as MgO and Al ₂ O ₃ , halides such as NaCl and CaF ₂ , sulfides such as CaS and PbS, carbonates such as Na ₂ CO ₃ and CaCO _{3, and the} like. Moreover, the mixture containing these 2 or more types may be sufficient.

Furthermore, it is preferable to use the nonmetallic melt containing 10% by mass or more of Al ₂ O ₃ . When the non-metallic melt and the nozzle refractory come into contact with each other, the refractory may be melted. However, when a non-metallic melt containing 10% by mass or more of Al ₂ O ₃ is used, it is a main component of the refractory. This is because Al ₂ O ₃ does not dissolve, so that melting damage can be prevented.

Specific examples of the non-metallic melt include Na ₃ AlF _6- (60% by mass), CaF _2- (22% by mass), Al ₂ O _3- (18% by weight) mixed so that the melting point is 867 ° C. ), PbF ₂ — (45 mass%) mixed to have a melting point of 500 ° C., PbO— (55 mass%), or Na ₃ AlF mixed to have a melting point of 960 ° C. Those composed of _6- (90% by mass), Al ₂ O _3- (10% by weight) can be used.

  The non-metallic melt that prevents the air from being entrained in the nozzle can be interposed in various structures between the nozzle joint surface and a packing material made of an indeterminate refractory material or a flame retardant material. For example, a recess may be provided on the joint surface above the nozzle, and the recess may be filled with a nonmetallic melt. In this case, it is not necessary to newly install equipment to hold the nonmetallic melt.

  More specifically, as shown in FIG. 2, as an example of a structure in which the nozzle joint portion holds a non-metallic melt by a packing material 9 made of a refractory raw material or an amorphous refractory and an immersion nozzle 7, for example, The immersion nozzle 7 and the lower tundish nozzle are formed by installing a weir 11 on the upper surface of the immersion nozzle 7 and filling the space provided between the packing material 9 and the weir 11 with the liquid non-metallic melt 10. 4 can be sealed.

In addition, as shown in FIG. 3, a liquid non-metallic melt 10 can be filled and sealed between refractory sealing materials 9a and 9b having the same planar shape and a double circumferential structure.
Moreover, as the packing material 9, what knead | mixed the refractory raw material with the thermosetting resin can be used. It has plasticity at room temperature and is compressed when a force is applied in the vertical direction to join the immersion nozzle to the lower tundish nozzle. At this time, the liquid non-metallic melt 10 accommodated in the gap of the packing completely fills the gap, which is preferable.

  Moreover, as shown in FIG. 4, the circumferential recessed part 12 can also be provided in the joining surface of an immersion nozzle upper part. If the volume of the liquid non-metallic melt 10 is excessive with respect to the volume of the gap in the packing, the liquid may overflow and the sealing performance may deteriorate. The amount of the melt 10 can be increased, and the sealing performance can be further improved, which is preferable.

  Moreover, as shown in FIG. 5, the circumferential recessed part 12 can also be provided in the joint surface of a tundish lower nozzle bottom part. When the volume of the liquid sealing material is excessive with respect to the volume of the gap of the packing, the liquid non-metallic melt 10 enters the concave portion 12 at the upper portion, so that it is possible to prevent the liquid from overflowing and the sealing performance from being lowered.

  In addition, the joining method and the structure of the joining part of the present invention as described above are not limited to the joining part between the tundish lower nozzle and the immersion nozzle, but airtightness such as joining between the pan sliding nozzle and the long nozzle. Of course, it can be applied to all joints between refractories that are required.

In the continuous casting equipment for steel composed of a combination of tundish upper nozzle, sliding nozzle, tundish lower nozzle and immersion nozzle, the seal member shown in Table 1 is used, and the tundish lower nozzle and immersion nozzle are joined. Operated. Table 2 shows the composition (% by weight) of the nonmetallic melt and the melting point of each.
The operating conditions were a casting speed of 1.7 m / min, a steel casting width of 1200 mm, a casting thickness of 248 mm, and 1350 tons of molten steel was cast. The components of the molten steel are C = 20 ppm, Si = 0.01%, Mn = 0.2%, P = 0.02%, S = 0.01%, Al = 0.015%.

Further, as a comparative example, the sealing member was joined only with a packing material without using a non-metallic melt, and the other was continuously cast steel under the same conditions as in the examples.
In order to evaluate defects caused by atmospheric suction, the slab surface was stepped and the number of bubble defects was counted. The bubble defect here refers to a defect in which bubbles or inclusions are aggregated via bubbles among the defects observed by visual observation. Moreover, in order to quantify the amount of oxidation by the sucked air, changes in the Al concentration in the molten steel in the tundish delivery side and the mold were measured.

  In the examples, sealing between the tundish lower nozzle and the immersion nozzle with a non-metallic melt can prevent air from being sucked in, and as a result, it can be confirmed that neither air bubble defects nor defects due to alumina clusters occur. It was. In addition, nozzle clogging did not occur.

In Comparative Example 1, since casting was performed using only the packing material, air was sucked from the joint, and bubble defects were generated on the slab surface. Moreover, Al in the molten steel was oxidized, and nozzle clogging with alumina clusters occurred.
In Comparative Example 2, since the packing material containing Al was used, the oxidation of Al in the molten steel did not occur due to the fixation of oxygen by Al, but air bubble defects occurred on the slab surface due to the suction of air. did.

It is a schematic diagram of the ladle used for continuous casting, a long nozzle, a tundish, and an immersion nozzle. It is a front view which shows embodiment of this invention. It is a longitudinal cross-sectional view of the junction part of the tundish lower nozzle for continuous casting of this invention, and an immersion nozzle. It is a longitudinal cross-sectional view of the junction part which shows other embodiment. It is a longitudinal cross-sectional view of the junction part which shows other embodiment. It is a longitudinal cross-sectional view of the junction part which shows other embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ladle 2 Upper plate of sliding nozzle 3 Middle plate of sliding nozzle 4 Lower plate of sliding nozzle 5 Long nozzle 6 Tundish 7 Immersion nozzle 8 Mold 9 Packing material 9a Outer part of double annular packing material 9b Inner circumference of double annular packing material Part 10 Liquid non-metallic melt 10a Molten aluminum or Al alloy layer 11 Weir 12 Circumferential recess

Claims (4)

  A method for sealing a nozzle joint in a steel continuous casting facility, wherein the nozzle joint is sealed with a non-metallic melt to prevent air entrainment in the nozzle. Nozzle joint sealing method. The method for sealing a nozzle joint in a steel continuous casting facility according to claim 1, wherein a nonmetallic melt containing 10% by mass or more of Al ₂ O ₃ is used.   This is a seal structure for nozzle joints in continuous casting equipment for steel, in which air is entrained between the packing material made of irregular refractories and flame retardant materials and the nozzle joint surface to be joined. A seal structure for a nozzle joint in a continuous casting equipment for steel, wherein a non-metallic melt to be prevented is held.   The nozzle joint seal structure according to claim 3, wherein a concave portion is provided on a joint surface of an upper portion of the nozzle, and the nonmetallic melt is filled in the concave portion.

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