JP2005193281A - Upper nozzle with interior ring - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce an inner hole melting loss caused in oxygen cleaning after casting, in an upper nozzle having an interior ring in a sliding nozzle (SN). <P>SOLUTION: The upper nozzle 1 comprises: an upper nozzle main body 2; and the interior ring 3 attached to an enlarged diameter section 6 formed by a step in an inner hole of the upper nozzle main body via a mortar 4. An SN upper plate 8 arranged on a low surface of a ring via the mortar 4 is attached on a bottom of a ladle of the upper nozzle 1. The interior ring 3 is replaced in such a way that the upper plate 8 is removed, and the interior ring 3 is pulled down from the enlarged diameter section 6. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an upper nozzle structure used in a sliding nozzle (SN) apparatus in continuous casting of molten steel, and more particularly to an upper nozzle having an interior ring.

  The upper nozzle, upper plate, lower plate, lower nozzle, etc. that make up the SN device are required to have excellent corrosion resistance, oxidation wear resistance, thermal shock resistance, etc. as refractories. Alumina-carbon refractories are widely used.

  In particular, the SN device provided in the ladle is subjected to an oxygen cleaning operation by blowing oxygen to always remove the metal attached to the upper nozzle inner hole and the upper plate inner hole after casting.

  This oxygen cleaning work is to exothermic oxidization and removal of the metal attached by blowing oxygen from an iron lance pipe, but a large amount of high-temperature molten FeO is generated, which reacts with the refractory, and in particular, The inner hole of the upper nozzle is significantly melted. As the number of times of use increases, the amount of erosion increases, and the diameter of the nozzle holes of the upper plate and the upper nozzle is enlarged, so that the stability of the flow rate control cannot be maintained. Moreover, the remaining thickness of the dowel part of the upper plate is reduced, and the risk of leakage of molten steel is increased.

  For this reason, various measures have been taken in the past to prevent the nozzle holes from being melted by this oxygen cleaning operation.

  For example, in Patent Document 1, after the inner hole of the worn upper nozzle is cleaned with oxygen, an inner ring made of a cylindrical refractory is inserted, and mortar is filled between the inner wall of the nozzle hole and the inner ring. It is described that an interior ring is attached. However, since the inner ring is attached by mortar filled in the uneven surface of the inner hole caused by the melting damage during oxygen cleaning, the joint thickness varies due to mortar, and the stress absorption due to thermal expansion is insufficient. And problems such as poor mounting state of the interior ring occur. Furthermore, since the interior ring is supported in a free state without a support mechanism, there is a problem that the interior ring is easily dropped. In addition, depending on the form of erosion of the upper nozzle, it is necessary to fill the mortar from the upper part, that is, from the inside of the ladle, which requires much labor. Furthermore, high alumina, fused silica, zircon, or clay is used as the material of the cylindrical refractory, but these refractories do not have sufficient durability against oxygen cleaning.

Patent Document 2 discloses that the upper nozzle is composed of a densified alumina carbonaceous material containing 20 to 40% by weight of calcined alumina and 5 to 25% by weight of metal powder. It is described that the matrix is densified by the action of the above to improve resistance to molten FeO and to reduce melting loss. As a result, although the durability of the upper nozzle has been significantly improved in terms of material, it is necessary to further suppress melting damage due to oxygen cleaning in order to increase the number of uses.
JP 55-54261 A Japanese Patent Laid-Open No. 11-246264

  A first object of the present invention is to reduce inner hole melting damage during an oxygen cleaning operation after casting in an upper nozzle having an interior ring in an SN device.

  Another object is to provide an upper nozzle equipped with an interior ring that can eliminate the influence of melting damage on the upper nozzle body.

  Furthermore, the other subject is providing the upper nozzle which installed the interior ring so that replacement | exchange was possible in the upper nozzle equipped with the interior ring.

  Another object is to provide an upper nozzle structure in which a ring is reliably restrained without variation in joint thickness due to mortar between upper nozzle bodies.

  Furthermore, another object is to provide an upper nozzle that can easily replace the interior ring even when the SN device is in an operating state.

  The present invention is an upper nozzle structure of a sliding nozzle device used for continuous casting of molten steel, wherein a diameter-enlarged portion having a step is formed at a downstream end portion of an inner hole surface of an upper nozzle body, and the inside of the enlarged-diameter portion is formed. A magnesia-chrome ring-shaped refractory is mounted through a mortar.

  The diameter-enlarged portion having a step is a portion where the inner diameter is enlarged by the step, and the inner hole is linearly formed from the step start portion of the downstream-side enlarged portion to the lower end surface by one step. Moreover, the enlarged diameter portion may be inclined so that the inner hole diameter increases in the downstream direction.

  The inner ring has a structure in which the upper end surface of the inner ring is securely constrained to the stepped surface of the inner hole of the upper nozzle body, and the lower end surface of the inner ring is reliably constrained to the upper surface of the dowel portion of the plate. In addition, when replacing the upper plate body, the lower end surface of the inner nozzle fitted to the enlarged diameter part of the upper nozzle is exposed, and there is no restriction, so the used (melted) inner ring can be easily replaced with a new one. Can be exchanged. Therefore, this ring can replace only the interior ring even in a so-called use state where the upper nozzle is installed in the SN device.

  The material of the ring is preferably magnesia chrome due to FeO resistance, thermal shock resistance, oxidation resistance, molten steel wear resistance, and the like. Usually, nozzles having molten steel passage holes such as an upper nozzle, a lower nozzle, and a plate are required to have very strict spalling resistance, and in recent years, most of them only use refractories by carbon bonding. By using a carbon bond, the modulus of elasticity and the coefficient of expansion are reduced, so that it is natural that the durability is remarkably superior to that of a refractory that does not contain carbon. However, in the present invention, it has been found that magnesia chromium having no carbon bond can be sufficiently applied, and that carbon-containing bricks such as alumina carbon, magnesia carbon, spinel carbon, and spinel are superior. .

  However, the magnesia-chromium constituting the interior ring has excellent oxidation resistance and FeO resistance, but has the disadvantage of being inferior in spalling resistance. This magnesia-chromium mounting structure to the upper nozzle body reduces the disadvantages of magnesia-chromium, making it more durable than other materials, taking advantage of its superior resistance to oxidation and FeO. improves. Moreover, the inner plate melting loss of the upper plate is greatly reduced.

  As the magnesia chromic material, any material of magnesia chrome brick generally used as a refractory for steelmaking, cement rotary kiln, waste melting furnace and the like can be used without any problem.

  As a mortar, it is generally used when installing an upper nozzle against tuyere bricks in a ladle or tundish between continuous casting nozzles, or when installing a porous plug against tuyere bricks. Mortar can be used. Such a mortar has the advantage that it is difficult to seize, and can be removed easily when removing and attaching the ring. Specifically, it is easy to use a mortar containing carbon, which is made of a raw material powder such as alumina, which is relatively difficult to sinter, and that uses water glass or phosphoric acid as a binder. Moreover, it is also possible to use a sheet-like or plate-like mortar.

  The joint thickness of the mortar is preferably 0.5 to 3 mm. If the joint thickness is less than 0.5 mm, the absorption of stress caused by expansion in the height direction and thickness direction of the ring is small, compressive stress is generated in the ring itself, and tensile stress is generated in the matrix, and the ring collapses. Or, a crack occurs in the mother body. Moreover, when joint thickness exceeds 3 mm, the insertion of the metal ingot and molten FeO from a nozzle inner hole part will become remarkable, and the danger which will lead to the leakage of molten steel from the molten damage of a joint part will become high. By providing such joints, the expansion allowance of the ring-shaped refractory is absorbed, and the stress is reduced.

  The upper nozzle of the present invention is provided with a diameter-enlarged portion having a step in the normal upper nozzle, but this can be formed by a mold at the time of molding, or can be processed by a lathe after molding and heating. it can. A magnesia chromic ring can also be made in the same manner. And the ring after baking is normally set with the mortar to the upper nozzle after heating or baking.

  The upper nozzle structure of the present invention has a structure in which only the interior ring below the upper nozzle is exchanged, and the material of the interior ring is made of magnesia chrome, thereby dramatically improving the durability of the upper nozzle. The upper plate can also suppress the melting damage of the dowel part. As a result, the operating conditions of the flow rate control are stabilized, a significant cost reduction is achieved, and safety against leakage steel is further improved.

  In the upper nozzle structure of the present invention, the inner hole of the upper nozzle body, in particular, the inner surface of the enlarged diameter portion to which the inner ring is attached does not melt. For this reason, even when replacing with a new interior ring, there is almost no variation in joint thickness between the upper nozzle body and the interior ring, and accurate mounting becomes possible.

  Hereinafter, embodiments of the present invention will be described by way of examples.

  FIG. 1 shows a longitudinal sectional view of the upper nozzle 1 of the present invention.

  In the figure, the upper nozzle 1 includes an upper nozzle body 2 and an interior ring 3 disposed in an inner hole of the upper nozzle body via a mortar 4. The cylindrical inner ring 3 is attached to an enlarged diameter portion formed in the inner hole 5 of the upper nozzle body 2.

  This enlarged diameter portion is shown as 6 and is formed by a step provided in the inner hole 5 of the upper nozzle body.

  The inner surface of the enlarged diameter portion 6 is linearly formed to the lower end portion, and the inner diameter is formed so that the lower end portion is slightly larger than the upper end portion. And the inner ring 3 also has a lower end diameter slightly larger than the upper end portion, for example, the upper end outer diameter is 120 mm, the lower end outer diameter is 122 mm, and the height is 60 mm on average. The wall thickness is adjusted to 22 mm. By doing so, when the ring is mounted from the lower side of the nozzle, the filling property of the mortar 4 is improved.

  Further, reference numeral 61 denotes a recess formed in the lower end surface of the enlarged diameter portion 6 for mounting the dowels of the upper plate 8 shown in FIG.

  FIG. 2 shows an example in which the upper nozzle 1 shown in FIG. 1 is mounted through the mortar 4 in the inner hole of the tuyere brick 7 at the bottom of the pan.

  Reference numeral 8 denotes an SN upper plate disposed on the lower end surface of the upper nozzle 1 via a mortar 4.

  The upper plate 8 is pressed upward by a lower plate (not shown), and the dowel portion 81 of the upper plate 8 is mounted in a recess formed on the lower end surface of the enlarged diameter portion 6. Accordingly, the vertical movement of the interior ring 3 attached to the enlarged diameter portion 6 of the upper plate 8 via the mortar 4 is restricted.

  When replacing the interior ring 3, the interior ring 3 can be easily removed from the main body of the upper nozzle 1 by removing the upper plate 8 and pulling it out as it is, or by breaking it with a breaker or the like.

  After the existing interior ring 3 is removed, the mortar remaining on the inner surface of the enlarged diameter portion of the upper plate body is removed. Thereafter, mortar can be applied to the upper end surface and the outer peripheral surface of the new interior ring for replacement, and can be mounted by a simple operation of inserting from the lower side of the figure.

  The inner ring is cylindrical, but its size should not be too large in terms of spalling resistance and oxygen cleaning resistance. More preferably, the inner ring has an outer diameter of 150 mm or less, a height of 50 to 150 mm, and a wall thickness of 10 to 25 mm.

  If the outer diameter is large, there is a problem that the spalling resistance is lowered, and it is preferably 150 mm or less. The lower limit is a size obtained by adding the thickness of the inner ring to the size of the nozzle hole. Generally, 40 mm or more is more preferable. The height of the interior ring is preferably 50 mm or more and 150 mm or less in consideration of the size of the erosion caused by oxygen cleaning and the spalling resistance. If it is less than 50 mm, it becomes difficult to cover the damaged part due to oxygen cleaning, and if it exceeds 150 mm, the spalling resistance is deteriorated. The wall thickness is preferably 10 to 25 mm, and if it is less than 10 mm, there is a problem with the strength of the interior ring, and if it exceeds 25 mm, the spalling resistance decreases. If the outer diameter of the upper nozzle and the inner ring are made to have a small outer shape at the tip, the inner ring can be easily inserted, and the mortar can be filled more easily.

  In the upper nozzle 1 shown in FIG. 1, an interior ring 3 made of the material shown in Table 1 was attached, and each was attached to a ladle for testing.

  Example 1 is a direct bond magnesia chrome, Example 2 is semi-ribboned magnesia chrome with a different chemical composition from Example 1, Comparative Example 1 is a non-fired alumina carbon, and Comparative Example 2 is low in graphite-free Carbon type unfired magnesia carbon, Comparative Example 3 is a low carbon type unfired magnesia carbon containing graphite, Comparative Example 4 is fired high alumina, and Comparative Example 5 is fired magspinel.

The test was carried out in the SN ladle of the actual ladle, washed with oxygen after each casting, and then the state of erosion of the inner ring of the upper nozzle was visually observed. The average damage dimension of the interior ring was calculated. Evaluation was made based on the average damage size of the interior ring.

  In the interior rings of Examples 1 and 2 that are magnesia-chromium, the inner ring's inner holes were significantly less melted and cracks were slight compared to Comparative Example 1. From the melting rate and the inner ring wall thickness of 22 mm, it was found that the usable number of times can be nearly double that of the current material.

  Since the magnesia carbon material containing no graphite, which is Comparative Example 2, has a high coefficient of thermal expansion, cracks due to spalling occur on the working surface, and the magnesia particles fall off, resulting in large wear of the inner holes and the number of usable times. The result was inferior.

  Although the magnesia carbonaceous material containing graphite as Comparative Example 3 had slight cracks on the working surface, the inner hole was greatly worn out due to sag due to oxidation, and improvement in the number of usable times was not recognized.

The fired high-alumina material of Comparative Example 4 had slight cracks on the operating surface, but because it contains molten FeO and a SiO ² component that generates a low-melting-point material, the melting loss was large and no improvement was observed. . In the fired mag spinel of Comparative Example 5, the wear was increased due to the dropping of the aggregate particles from the cracks on the working surface, and no improvement in the number of usable times was observed.

  The upper nozzle of the present invention is suitable for an SN device for continuous casting of molten steel, and can be used in a ladle or tundish.

The longitudinal cross-sectional view of the upper nozzle which has an interior ring of this invention is shown. The longitudinal cross-sectional view of the state which set the upper nozzle of this invention to the tuyere brick of the pan is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Upper nozzle 2 Upper nozzle body 3 Interior ring 4 Mortar 5 Inner hole of upper nozzle 6 Expanded diameter part 61 Recessed part provided in the lower end of the enlarged diameter part 7 Feather brick 8 Upper plate 81 Dowel of upper plate 9 Gold of SN device Frame 10 Ladle bark

Claims (2)

  An upper nozzle having an inner ring in which a diameter-increased portion having a step is formed at a downstream end portion of an inner hole of the upper nozzle, and a cylindrical magnesia-chromic inner ring is mounted in the enlarged diameter portion via a mortar.   2. The upper nozzle having an inner ring according to claim 1, wherein the enlarged diameter portion has an inner diameter enlarged by one step formed on the inner hole surface of the upper nozzle, and is linear from the step position to the lower end surface.

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