JP2015113489A - Dip tube for use in refining apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dip tube for use in a refining apparatus, having shaped refractories arranged to cover the lower end part of a cylindrical mandrel, with a structure to prevent occurrence of large cracks in the shaped refractories and falling of the shaped refractories.SOLUTION: The dip tube includes shaped refractories 20 at least in the lower end part. The shaped refractory 20 include a groove 21 in which the lower end part of a mandrel 10 is inserted, and a castable refractory 30 applied into the groove. The inner surface of the groove 21 includes a recess 21a having an arc-shaped longitudinal section. In the longitudinal section passing the deepest part of the recess 21a, the length of the recess 21a is represented by L. The center location of the tip of a supporting hardware 11 projecting from the mandrel 10 is set to within 0.3L from the horizontal line connecting from the deepest position of the recess 21a, normal to the surface of the mandrel 10.

Description

  The present invention relates to a dip tube used in a molten metal refining apparatus.

  CAS (Composition Ajustment by Sealed Argon Bubbling), which adjusts the composition of the molten steel in the ladle through a dip tube, for the secondary refining of molten steel that has been refined in a converter, etc. A degassing device such as RH (Ruhrstahl-Heraus) or DH (Dortmunt-Horde) is used which sucks up the degassing device and degass it and returns it to the ladle side.

  The dip tube connected to the secondary refining equipment that processes these molten steels basically has a structure in which a refractory is provided on the inner and outer surfaces of a cylindrical cored bar. However, since at least the tip is immersed in the molten steel and slag during refining of the molten steel, the slag has a large melting loss and a short life. Therefore, a fixed pipe refractory such as magnesia-chromic brick or magnesia-carbon brick, which has better durability than an irregular refractory, is placed at the part in contact with slag or molten steel, so as to obtain a dip tube that suppresses melting damage. Became.

  However, when the refining process in the secondary refining apparatus is completed, the dip tube is withdrawn from the liquid surface of the molten steel and slag in the ladle, and the process proceeds to the next refining process. That is, the dip tube is exposed to molten steel having a temperature of over 1600 ° C. during the refining process, and is exposed to the outside air between the processes, so that rapid heating and cooling are repeated. If this repetition is continued, cracks will occur in the regular refractory and the irregular refractory.

  In general, the irregular refractory is fixed to the core with multiple metal studs, whereas the fixed refractory is not easy to install the stud and is attached to the core with mortar. The fixing force is relatively small. For this reason, if a crack occurs in the regular refractory, the regular refractory is likely to fall off, which may deteriorate the life of the dip tube.

  Therefore, in Patent Document 1, in a dip tube of a degassing apparatus in which a refractory is provided on the inner and outer surfaces of a cylindrical core metal, a groove in which the core metal enters the core refractory at the lower end of the dip tube and the thickness of the core metal A locking hole communicating with the fixing hole formed in the direction is provided, the cored bar is inserted into the groove of the standard refractory, and the fixing pin is inserted into the fixing hole and the locking hole to connect the cored bar and the standard refractory. A fixed structure has been proposed. Patent Document 2 states that the refractory around the metal core is an irregular refractory, the regular refractory is arranged below the irregular refractory, and both are joined with studs, and the regular refractory falls off at the stage of use. Preventing structures have been proposed.

  In Patent Document 3, a regular refractory is arranged from the upper part to the lower part of the inner surface of the dip tube, an irregular refractory is arranged between the core metal and the regular refractory, and the irregular refractory is made of metal. A structure has been proposed in which a fixed refractory is fixed to a boundary surface with an irregular refractory by irregularities that are partially formed in a concave shape or a convex shape.

JP 2010-248557 A JP 2011-074439 A JP 2008-127777 A

  In the dip tube of Patent Document 1, since the entire weight of the shaped refractory is applied to the portion locked and fixed by the fixing pin, the point where cracks are likely to occur in advance from the portion, and the molten steel immersed in the molten steel during refining When cracks occur in the fixed refractory in the immersion part, there is a concern that the support effect is reduced below the crack and the fixed refractory is likely to fall off. The dip tube of Patent Document 2 has a structure in which a stud is directly arranged inside a regular refractory, and there is a problem that a crack is likely to start from a contact point between the stud and the regular refractory.

  Further, in the dip tube of Patent Document 3, due to the fact that the thermal conductivity of each of the regular refractory, the irregular refractory, and the stud is greatly different, there is a temperature difference around the uneven part and the stud during use. There has been a problem that cracks are likely to occur due to the thermal stress generated by the temperature difference.

  Therefore, the problem to be solved by the present invention is a structure capable of preventing the occurrence of cracks and dropping off of a regular refractory in a dip tube for a refining apparatus in which a regular refractory is arranged so as to cover the lower end portion of a cylindrical metal core. Is to provide.

  In order to solve the above-mentioned problems, the present inventor, in a dip tube for a refining apparatus in which a fixed refractory is arranged so as to cover the lower end portion of a cylindrical metal core, a support metal fitting is provided in a groove provided in the fixed refractory. The result of repeated investigations focusing on the shape of the groove and the positional relationship of the support hardware in this structure by adopting a structure that inserts the lower end of the cored bar and constructing an irregular refractory in the groove The present invention has been completed.

That is, this invention provides the dip tube for the following refining apparatuses.
(1) A dip tube for a refining apparatus in which a refractory is provided on the inner and outer surfaces of a cylindrical core metal, wherein at least the lower end of the dip tube is a regular refractory, and the groove is provided in the regular refractory. The lower end portion of the cored bar is inserted, and an irregular refractory is constructed in the groove. The groove has a hollow part with an arc-shaped longitudinal section on the inner surface, and the cored bar A support metal that protrudes in a radial direction from the surface, and in a longitudinal section passing through the deepest part of the hollow part, when the length of the hollow part is L, the circumference of the core metal from the deepest part position of the hollow part A dip tube for a refining apparatus in which the center position of the tip end portion of the support hardware is included in a range of 0.3 L from a horizontal line connected perpendicularly to the surface.
(2) The dip tube for a refining apparatus according to (1), wherein the fixed refractory is disposed at a site that is locally damaged during refining.

  Thus, the dip tube of the present invention has a longitudinal section on the inner surface of the groove in the structure in which the lower end portion of the metal core is inserted into the groove provided in the fixed shape refractory at the lower end portion and the amorphous refractory is constructed in the groove. By providing a hollow portion having an arcuate shape so that the regular refractory is in contact with the irregular refractory by the arcuate hollow portion, the regular refractory can be prevented from falling off.

  Further, in the dip tube of the present invention, a support metal such as a stud protrudes in the radial direction from the peripheral surface of the core bar for the purpose of holding the irregular refractory in the groove. Here, when the dip tube is immersed in the molten metal during refining, heat is transferred toward the cored bar via the fixed surface refractory on the working surface side. In general, it is considered that heat is transferred preferentially toward the tip of the support metal adjacent to the fixed refractory. This means that the amount of heat transfer from the inner surface of the groove changes depending on the distance from the inner surface of the groove of the standard refractory to the tip of the support metal, resulting in a temperature difference depending on the location on the inner surface of the groove of the standard refractory. To do. This temperature difference is considered to be a difference in expansion of the regular refractory and cause local stress.

  For example, if the depressions (concave / convex) and studs are arbitrarily arranged as in the dip tube of Patent Document 3, the respective thermal conductivity greatly differs, so that there are no irregularities or studs around during use. A temperature difference occurred, and cracks were likely to occur due to the thermal stress generated by the temperature difference.

  The inventor of the present invention pays attention to the fact that these directly affect the occurrence of cracks and dropout of the fixed refractory, and adopts a configuration for reducing the temperature difference. That is, the dip tube of the present invention has the following: “In the longitudinal section passing through the deepest part of the hollow part, when the length of the hollow part is L, the position from the deepest part of the hollow part to the peripheral surface of the cored bar. The center position of the tip end portion of the support hardware is included within a range of 0.3 L from a horizontal line connected vertically. By this structure, the difference by the site | part of the distance from the groove | channel (dent part) inner surface of a fixed form refractory to the front-end | tip part of a support metal fitting can be made small, and the said temperature difference can be made small. From the point of making this temperature difference smaller, it is preferable that the said hollow part is made into the longitudinal cross-sectional shape along the circle centering on the front-end | tip part center position of the said support metal object.

  Thus, the dip tube of the present invention has a longitudinal section on the inner surface of the groove in the structure in which the lower end portion of the metal core is inserted into the groove provided in the fixed shape refractory at the lower end portion and the amorphous refractory is constructed in the groove. Preventing the occurrence of large cracks and falling off of a regular refractory by providing an arc-shaped recess and optimizing the positional relationship between the recess and the support hardware that supports the irregular refractory in the groove. And the life of the dip tube can be extended.

It is the longitudinal cross-sectional view which cut | disconnected the dip tube by Example 1 of this invention by the central axis. It is the figure which expanded the site | part which provided the regular refractory in the dip tube of FIG. It is a figure which shows the positional relationship of the hollow part of a fixed form refractory, and a support metal in Example 1 of this invention. In Example 4 of this invention, it is a figure which shows the positional relationship of the hollow part of a fixed form refractory, and a support metal object. It is a figure in the comparative example 1 of this invention which shows the positional relationship of the hollow part of a regular refractory, and a support metal object. It is a figure in the comparative example 2 of this invention which shows the positional relationship of the hollow part of a regular refractory, and a support metal object.

  As shown in FIG. 1, the dip tube of the present invention is a dip for a refining apparatus in which a refractory (a regular refractory 20 and an irregular refractory 30) is provided on the inner and outer surfaces of a cylindrical metal core 10 having a flange on the top. At least the lower end of the tube is a fixed refractory 20, the lower end of the cored bar 10 is inserted into a groove 21 provided in the fixed refractory 20, and the amorphous is formed in the groove 21 and the upper part of the fixed refractory 20. The refractory 30 is constructed.

  The groove 21 has a recess 21a having an arc-shaped longitudinal section on its inner surface, and the cored bar 10 has a bar-shaped support metal 11 protruding in the radial direction from its peripheral surface. And in this invention, when the length of the hollow part 21a is set to L in the longitudinal cross-section (FIG. 1) which passes through the deepest part of the hollow part 21a, it is perpendicular | vertical to the surrounding surface of the metal core 10 from the deepest part position of the hollow part 21a. The center position of the tip end portion of the support hardware 11 is included in the range of 0.3 L with respect to the horizontal line connected to the. 1 and 2, the support metal 11 located at the lowermost end is Y-shaped. However, in the support metal 11 having the tip branched in this way, the above-mentioned “tip center position” means the branched tip. This is the midpoint of a line connected by a straight line.

  In the above configuration, the fixed refractory 20 is in contact with the irregular refractory 30 through the arc-shaped depression 21a, and is thus firmly held on the core metal 10 via the irregular refractory 30 by the anchor effect of the depression 21a. Is done. Further, the amorphous refractory 30 is firmly held by the cored bar 10 by the support metal 11. Therefore, since the fixed refractory 20 is firmly held by the cored bar 10 via the irregular refractory 30, the fixed refractory 20 can be prevented from falling off.

  Further, in the present invention, by defining the positional relationship between the deepest position of the recess 21a and the center position of the tip of the support metal 11 as described above, the tip of the support metal 11 from the inner surface of the recess 21a of the fixed refractory 20 is provided. The difference by the part of the distance to the part is made small. Thereby, the "temperature difference" by the site | part of the groove | channel 21 inner surface of the fixed refractory 20 demonstrated previously can be made small, and the large crack generation | occurrence | production and dropping-off of the fixed refractory 20 can be prevented. That is, the heat transfer during the refining operation described above is reduced by reducing the “distance difference” (distance variation) depending on the portion from the inner surface of the hollow portion 21a of the fixed refractory 20 to the center position of the tip of the support metal 11. Accordingly, it is possible to prevent a phenomenon in which the temperature differs locally on the inner surface of the groove 21 of the fixed refractory.

  In the present invention, the reason why the vertical cross-sectional shape of the hollow portion 21a is an arc shape is that the above-mentioned "distance difference" is easy to reduce, and the hollow portion 21a is unlikely to become a starting point of cracks due to thermal stress. It is easy to make a shape in the manufacture of a regular refractory.

  The hollow portion 21a is made continuously over the entire circumference of the inner surface of the groove 21 or intermittently in the circumferential direction. When the depressions are intermittently formed, the width (circumferential length) of the depressions 21a is equal to or greater than the length L of the depressions 21a in the longitudinal section from the viewpoint of reducing the temperature difference in the horizontal direction. If it is enough. The length L of the recess 21a is suitably 20 mm or greater and 100 mm or less. If L is less than 20 mm, the temperature difference becomes large, and if it exceeds 100 mm, cracks due to the difference in thermal expansion between the regular refractory and the irregular refractory tend to occur in the regular refractory during use. It is preferable from the viewpoint of workability at the time of manufacturing that the length of the support metal 11 is set to a length that allows the core metal 10 provided with the support metal 11 to enter the groove 21. The depth of the recessed portion 21a, that is, the deepest position of the recessed portion may be L / 2 or more from the center position of the tip end portion of the support hardware 11.

  In the dip tube of the present invention, the boundary position between the slag and the molten metal, that is, the slag line is a part that is locally damaged during refining (local loss part). It is preferable to arrange a regular refractory having excellent corrosion resistance. Since the position of the slag line changes depending on various conditions such as the immersion depth of the dip tube, the local loss portion has a range corresponding to the change in the position of the slag line. Specific examples of the material of the fixed refractory 20 disposed in the local loss portion include a magnesia-carbon material and a magnesia-spinel-carbon material that have high corrosion resistance and excellent spalling resistance. A plurality of the fixed refractories 20 are arranged in a ring shape in the circumferential direction of the cored bar 10.

  On the other hand, as the amorphous refractory 30, an alumina or alumina-magnesia casting material is preferably used from the balance of workability, expansibility, thermal conductivity and strength.

  In each example and comparative example, the influence of the position of the support hardware on the temperature of the hollow portion of the regular refractory is calculated by calculating the temperature and thermal expansion of each part by simulation calculation, and the results of further actual furnace tests are shown in Table 1. Shown in

  In Table 1, the simulation calculation result of the temperature of the hollow part of the shaped refractory in each case is changed by changing the center position of the tip of the support metal 11 with respect to the deepest part position of the hollow part 21a as shown in FIGS. Indicated. In the figure, the position A is the uppermost end position of the recess 21a, the position B is the inner surface position of the recess 21a 45 ° below the position A, and the position C is the deepest position of the recess 21a.

  The simulation calculation was performed by applying a magnesia-carbon brick having a carbon content of 15% by mass as a regular refractory. This is because cracks occur due to thermal shock if the carbon content is low at the part immersed directly in the molten steel, and if the carbon content is high, there is a concern about carbon elution into the molten steel. This is because carbon brick is common. In addition, a high-alumina casting material was used as the amorphous refractory. This is to have fire resistance and to fill the space between the regular refractory and the core metal without any gap.

Thermal conductivity at 1000 ° C. of standard refractory (magnesia-carbon brick) is 17 W · m ⁻¹ · K ⁻¹ , and thermal conductivity at 600 ° C. of amorphous refractory (high alumina cast material) is 2 W · m ^{− The} calculation was performed assuming ¹ · K ⁻¹ , the temperature of the working surface of the fixed refractory in contact with the molten metal was 1600 ° C., and the temperature of the cored bar was 220 ° C. As the thermal expansion coefficient of each material at the temperature of the calculation result, data obtained by measuring the thermal expansion coefficient of each material in advance was used.

The thermal conductivity used for calculating the temperature in the table is measured according to the heat flow method described in JIS R 2616, and the coefficient of thermal expansion (%) is JIS R 2616.
Data measured under a nitrogen atmosphere according to the push rod method of R 2207 was used.

  The actual furnace test was performed for Example 1, Example 4, Example 5, Comparative Example 1 and Comparative Example 2.

  In the dip tube of the first embodiment shown in FIG. 1, the flange, the core metal 10 and the support metal 11 are integrated by welding, and this integrated product is inserted into the groove 21 of the standard refractory 20 to form the groove 21 and the standard refractory fire. It was manufactured by constructing an irregular refractory 30 on the top of the object 20. The regular refractory 20 was divided into 30 pieces in the circumferential direction, and its height was 500 mm. As the regular refractory 20 and the irregular refractory 30, the magnesia-carbon brick and the high-alumina cast material used in the simulation calculation were used, respectively. In addition, the groove | channel 21 and the hollow 21a were provided by processing after shaping | molding into a fixed form refractory.

  The groove 21 has a depth of 350 mm and a width of 82 mm. The recessed portion 21 a is provided continuously with the wall of the groove 21 so as to be concentric with the cored bar 10. The hollow portion 21a is a semicircle having a radius of 15 mm in longitudinal cross section, and the length L is 30 mm. The cored bar 10 has a thickness of 22 mm and an inner diameter of 1184 mm. The support metal 11 located on the side surface of the core metal is a cylinder having a length of 25 mm and an outer diameter of 10 mm. The support hardware 11 located at the lowermost end has a Y shape with an outer diameter of 5 mm and a length of 25 mm.

  The structures of Examples 2 to 4 and Comparative Examples 1 to 2 are the same as those of Example 1 except for the position of the support metal. The fifth embodiment is the same as the first embodiment except that the hollow portion is a semicircle having a longitudinal cross-sectional shape of a radius of 10 mm and a length L of 20 mm.

  These dip tubes were used in actual RH. The RH has two dip tubes, each of which is bolted with a flange structure. The two dip tubes flow argon gas, and the side that raises the molten steel is called the ascending side, and the opposite side is called the descending side. In this example, both the dip tube of the present invention and the comparative dip tube are on the descending side. used. At this time, the ladle contained an average of 410 tons of molten steel. Each ladle was counted as 1 ch and compared with the number of channels used until the life of the dip tube was replaced. The average treatment time per channel, that is, the time for which the dip tube was exposed to the molten steel was 17 minutes, and the time between treatments was 5 to 20 minutes.

  In Table 1, Example 1 is an example in which the center position of the tip end portion of the support metal 11 is aligned with a horizontal line perpendicularly connected to the peripheral surface of the cored bar 10 from the deepest position of the recess 21a as shown in FIG. The temperature difference between the C position and the A position is 86 ° C., and the difference in expansion coefficient at that time is 0.10. In the actual furnace test, it was replaced in 52ch. Although small cracks were seen in the regular refractory, they did not fall off, and the service life could be greatly improved.

  In Example 4, as shown in FIG. 5, the center position of the tip end of the support metal 11 is 0.3 L away from the horizontal line connected perpendicularly to the peripheral surface of the core bar 10 from the deepest position of the recess 21 a. The temperature difference between the A position and the C position is 433 ° C., and the difference in expansion coefficient is 0.48. Although small cracks of the regular refractory were seen, no dropout was seen, and the durability was good at 48 times.

  Example 5 is a case where L is 20 mm, and the center position of the tip end of the support metal 11 is 0.3 L away from the horizontal line connected perpendicularly to the peripheral surface of the core bar 10 from the deepest position of the recess 21a. The temperature difference between the A position and the C position is 137 ° C., and the difference in expansion coefficient is 0.15. Although small cracks of the regular refractory were seen, no dropout was observed, and the durability was 50 times, which was good.

  In the first comparative example, as shown in FIG. 5, the center position of the tip end of the support metal 11 is 0.4 L away from the horizontal line perpendicular to the peripheral surface of the core bar 10 from the deepest position of the recess 21 a. Yes, the temperature difference between the A position and the C position is as large as 551 ° C., and the difference in expansion coefficient is as large as 0.61. In the actual furnace test, a large crack occurred in the regular refractory, so it was replaced at 35ch.

  In Comparative Example 2, as shown in FIG. 6, the center position of the tip of the support metal 11 is 0.5 L away from the horizontal line connected perpendicularly to the peripheral surface of the core metal 10 from the deepest position of the recess 21 a. Yes, the temperature difference between the A position and the C position is as large as 653 ° C., and the difference in expansion coefficient is also as large as 0.72. In the actual furnace test, a large crack occurred in the regular refractory, and a part of the regular refractory dropped out.

  Although the illustrations of Examples 2 and 3 are omitted, in Example 2, the center position of the tip of the support metal 11 is 0 from the horizontal line that is perpendicularly connected to the peripheral surface of the cored bar 10 from the deepest position of the recess 21a. When the distance is 1 L, Example 3 is the case where the distance is 0.2 L. As compared with Example 4, the temperature difference and the expansion coefficient difference between the A position and the C position are small. Therefore, it is considered that a result superior to that of Example 4 can be obtained even in an actual furnace.

  Also, since the thickness of the fixed refractory is constant, there is almost no temperature difference in the vertical direction on the inner surface, so the temperature distribution is almost symmetrical with respect to the straight line connecting the center position of the tip of the support metal and the latest position of the recess. It is thought that. Therefore, from Table 1, the effect of the present invention can be obtained when the center position of the tip of the support metal is within 0.3 L from the horizontal line connected perpendicularly to the peripheral surface of the core metal from the deepest position of the depression. .

10 Core 11 Support metal 20 Fixed refractory 21 Groove 21a Recess 30 Unshaped refractory

Claims (2)

  A dip tube for a refining apparatus in which a refractory is provided on the inner and outer surfaces of a cylindrical core metal, wherein at least the lower end of the dip tube is a regular refractory, and the core metal is inserted into a groove provided in the regular refractory. A lower end portion is inserted, and an irregular refractory is constructed in the groove. The groove has a hollow portion with a circular cross-sectional shape on the inner surface, and the cored bar has a radius from the peripheral surface. In the longitudinal section passing through the deepest part of the hollow part, and having a length of the hollow part as L in the longitudinal section passing through the deepest part of the hollow part, from the deepest part position of the hollow part to the peripheral surface of the core metal A dip tube for a refining apparatus in which the center position of the tip end portion of the support hardware is included within a range of 0.3 L from a horizontal line connected vertically.   The dip tube for a refining apparatus according to claim 1, wherein the fixed refractory is disposed at a site that is locally damaged during refining.

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