JP6213441B2 - How to reuse tundish weir - Google Patents

Description

  The present invention relates to a method for reusing a refractory weir attached to a tundish for use in a continuous casting facility for steel and for controlling the flow of molten steel in the tundish.

  In continuous casting of steel, the molten steel in the ladle is once poured into the tundish, and with a predetermined amount of molten steel retained in the tundish, the molten steel is poured into the mold from the tundish to produce a slab. ing.

  The tundish not only has the function of supplying molten steel when changing the ladle when continuing continuous casting of multiple heat and the function of distributing molten steel to multiple molds, but also retains a predetermined amount of molten steel in the tundish. Therefore, the outflow amount of molten steel from the tundish to the mold is controlled with high accuracy, and furthermore, oxide-based nonmetallic inclusions such as deoxidation products suspended in the molten steel (hereinafter simply referred to as “inclusions”) It has functions such as flotation separation). In particular, it is widely practiced to install a weir in the tundish and control the flow of molten steel in the tundish to promote the floating separation of inclusions.

  Conventionally, after use, the tundish is cooled by water cooling or air cooling, etc., and then the ground metal and coating layer in the tundish (a coating made of magnesia powder applied to the surface of the work refractory forming the inner wall of the tundish The covering layer in which the material is applied with a thickness of several mm to several tens of mm), the weir, and the like are removed, and the weir and the coating layer are newly applied for the next use. The removed weir and coating material are crushed and then used as a solvent for decarburization and refining of hot metal in a converter, but most of them are disposed of as industrial waste. Then, the method of collect | recovering and reusing a used weir for the purpose of reducing the generation amount of a used refractory while reducing the amount of refractory used.

  For example, in Patent Document 1, a coating layer is formed on the surface of a tundish workpiece refractory, and then a weir made of a molded refractory is attached to the inside of the coating layer. After continuous casting, the weir is recovered from within the tundish. A method has been proposed in which a maintenance layer is formed on the surface of the work refractory on the inner wall of the tundish, and then the maintenance weir is attached inside the coating layer and reused.

  Normally, weirs (usually high alumina bricks) are constructed with mortar bonded to tundish work refractories (usually alumina-silica refractories), and the coating layer of magnesia powder is applied after weir construction. It is formed on the surface of the workpiece refractory by spraying or the like. When the weir having such a joint structure is forcibly removed from the tundish by, for example, lifting, the weir or the workpiece refractory is cracked or cracked and cannot be reused. On the other hand, the coating material made of magnesia powder has a characteristic that the shrinkage characteristic at the time of cooling is different from that of the tundish work refractory, and is easily separated from the work refractory due to a temperature drop after use.

  According to Patent Document 1, a coating material is interposed at the boundary between a tundish workpiece refractory and a weir, so that even if an excessive load is applied to the weir itself, the coating layer can absorb the load and break the weir. The recovery rate of reusable weirs will be improved.

JP 2012-183586 A

  However, Patent Document 1 has the following problems.

  In other words, the coating material itself has a characteristic that it is easy to peel from the workpiece refractory, unlike the tundish workpiece refractory, but the coating material itself is sandwiched between the weir and the workpiece refractory. The coating material that is used has a small temperature drop, so the amount of thermal shrinkage is small and does not peel off. If you try to forcibly remove the weir, the problem of cracking or cracking in the weir or work refractory still occurs To do. In other words, the recovery rate of reusable weirs is not high.

  The present invention has been made in view of the above circumstances, and the object of the present invention is to provide a highly probable weir with a shape that can be reused from a used tundish without damaging the work refractory of the tundish. It is to provide a method for reusing a tundish weir that can be recovered at the same time.

The gist of the present invention for solving the above problems is as follows.
[1] A method for reusing a tundish weir, wherein the weir is removed from the used tundish, the removed weir is placed in the tundish again, and the tundish is used in a continuous casting process of molten steel. The surface of the weir in the tundish weir and the inner wall of the tundish and the surface of the weir in the portion within 100 mm from the joining position are water-cooled, and this water cooling causes the surface temperature of the weir in the portion up to 100 mm from the joining position A method for reusing a tundish weir, wherein the temperature is lowered by 200 ° C. or more with respect to the temperature before the start of cooling, and then the weir is removed from the tundish.
[2] The metal weir is provided at the upper end of the weir, and the weir is lifted via the suspension and removed from the tundish. How to reuse the tundish weir.

  According to the present invention, the surface of the weir in a range within 100 mm from the joining position with the inner wall of the tundish is water-cooled, and the surface temperature of the weir in this range is lowered by 200 ° C. or more with respect to the temperature before the start of cooling. Is peeled from the inner wall of the tundish by heat shrinkage, and the weir can be easily removed from the tundish. As a result, it is possible to recover the reusable weir with high probability without damaging the tundish workpiece refractory.

It is side surface sectional drawing which shows an example of the tundish used with the 2 strand type slab continuous casting installation with which the reuse method of the tundish weir concerning this invention is applied. It is a figure which shows the condition which is cooling the edge part by the side of a joining position with the irregular refractory of a weir with the cooling water injected from a water cooling apparatus. It is a figure which compares and shows the collection rate of the reusable weir among the collect | recovered weirs by the example of this invention and a comparative example.

  Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a side cross-sectional view showing an example of a tundish used in a two-strand slab continuous casting facility to which the tundish weir reuse method according to the present invention is applied.

  As shown in FIG. 1, the tundish 1 has a shell 2 as an outer shell, and a permanent brick 3 made of molded brick is constructed on the inner surface side of the iron shell 2, and on the inner surface side of the permanent brick 3. An irregular refractory 4 is constructed as a work refractory. In the tundish 1, two weirs 6 made of molded bricks are placed opposite to each other with the central portion in the longitudinal direction of the tundish 1 interposed therebetween. The weir 6 has a width that covers the entire surface of the tundish 1 in the width direction and a height that is higher than the molten steel height in the tundish, and forms an inner wall of the tundish 1 by mortar (not shown). Bonded and fixed to the object 4. A plurality of dam holes 6 a for passing molten steel are provided in the lower portion of the dam 6.

  A coating layer 5 having a thickness of 10 to 30 mm of a coating material made of magnesia powder is formed on the inner surface side of the amorphous refractory 4 by spraying or the like. The coating layer 5 prevents the direct contact between the amorphous refractory 4 that is a workpiece refractory and the molten steel, and cleans the molten steel by utilizing the properties of MgO that the oxygen potential is low and the reaction with the molten steel is low. Is to maintain and promote

  On both ends of the tundish 1, a nozzle receiving brick 7 that is fitted to the permanent tension brick 3 and the irregular refractory 4 is disposed, and an upper nozzle 8 is installed by being inserted into the nozzle receiving brick 7. Below this upper nozzle 8, a sliding nozzle 9 for adjusting the flow rate of molten steel, which is composed of a fixed plate 10 and a sliding plate 11, is disposed. Further, below the sliding nozzle 9, molten steel is injected into a mold (not shown). An immersion nozzle 12 is provided for this purpose. The tundish 1 is provided with a lid, which is omitted in FIG.

  As described above, the tundish 1 is separated into three parts of a molten steel injection part 1A surrounded by two opposing weirs 6 and a molten steel discharge part 1B on both sides thereof, and a ladle (not shown) The molten steel injected into the molten steel injection part 1A flows into the molten steel discharge part 1B through the weir hole 6a provided in the weir 6. In a state where a predetermined amount of molten steel stays in the molten steel injection part 1A and the molten steel discharge part 1B, the molten steel staying in the molten steel discharge part 1B is injected into the mold through the upper nozzle 8, the sliding nozzle 9 and the immersion nozzle 12, Continuous casting of molten steel is performed.

Since the permanent brick 3 does not come into direct contact with the molten steel and is hardly damaged during use, the permanent brick 3 is used semipermanently unless it is broken by an impact during tundish dismantling. Since the permanent brick 3 has a small heat load, a silica-alumina refractory (for example, a waxy brick) having an Al ₂ O ₃ content of 45% by mass or less is usually used. On the other hand, the amorphous refractory 4 as the work refractory is worn away every time it is used, and is dismantled when a predetermined thickness cannot be secured, and is newly constructed each time. Since the amorphous refractory 4 is also generated when it comes into direct contact with molten steel, it is generally a high-alumina amorphous refractory which is an alumina-silica refractory containing 50% by mass or more of Al ₂ O ₃ . Is used.

  The weir 6 is in direct contact with the molten steel, and a heat insulating agent is put on the molten steel surface in the tundish, and the heated heat insulating agent is in the form of an oxide slag. High alumina bricks with excellent erosion properties are used. In FIG. 1, the amorphous refractory 4 is applied as the workpiece refractory, but the workpiece refractory is not limited to the amorphous refractory 4, and a molded alumina-silica-based high alumina material is used. It may be a molded brick.

  The tundish 1 used in the continuous casting process of steel is transported to the tundish maintenance station after discharging molten steel and slag remaining in the tundish 1 as necessary. At the tundish maintenance site, the tundish 1 is primarily cooled by spraying or spraying cooling water into the tundish with the lid removed.

  With this primary cooling, it is possible to cool the entire tundish to a certain temperature, for example, until the surface temperature of the irregular refractory 4 and the weir 6 reaches about 500 ° C., but the primary cooling is excessively performed. Then, cracks (called “heat cracks”) occur in the amorphous refractory 4 due to thermal contraction, and this thermal crack causes a problem that the life of the irregular refractory 4 is reduced. It is preferable to water-cool only the end portion on the joint position side with the unshaped refractory material 6. As a matter of course, the primary cooling may be performed only in the air without cooling with water. However, since the cooling time of the tundish 1 becomes long and the maintenance cycle time of the tundish becomes long if it is left to cool in the air, it needs to have a large number of tundish when it is left to cool in the air. There is.

  If the surface temperature of the irregular refractory 4 and the weir 6 of the tundish 1 is lowered to about 400 to 600 ° C. by the primary cooling, the junction position between the weir 6 and the irregular refractory 4 and the junction position is within 100 mm. The surface of the partial weir 6 is cooled with water. The reason for cooling the surface of the weir 6 after the surface temperature of the irregular refractory 4 and the weir 6 of the tundish 1 is lowered to about 400 to 600 ° C. is that This is to avoid work in a high-temperature atmosphere at the same time that the amorphous refractory 4 is easily separated.

  FIG. 2 shows a situation where the end of the weir 6 on the joint position side with the amorphous refractory 4 is cooled by the cooling water sprayed from the water cooling device. In FIG. 2, the permanent brick 3 and the coating layer 5 of the tundish 1 are omitted. As shown in FIG. 2, the water cooling device 13 has a water flow header 13a and a support base 13b attached to the water flow header 13a, and the cooling water supplied to the water flow header 13a is supplied to the water flow header 13a. It is configured to be jetted toward the weir 6 through the two nozzle holes 13c provided. Specifically, in the state where the left and right support bases 13b are overlaid on the iron skins 2 on the opposite long sides of the tundish 1, the jet of cooling water 14 from the nozzle hole 13c It is comprised so that it may inject to the edge part side of the joining position side with the thing 4. FIG.

  The cooling water jet 14 jetted from the water cooling device 13 toward the upper surface of the weir 6 cools the upper surface of the weir 6 and then cools both side end portions of the weir 6 while flowing down both side surfaces of the weir 6. It reaches the bottom of the weir 6. Since the amorphous refractory 4 at the bottom of the tundish 1 has a high temperature of 400 to 600 ° C., the cooling water reaching the bottom of the weir 6 evaporates. However, although the cooling water reaching the bottom of the weir 6 evaporates, if a large amount of cooling water is supplied, the cooling water may stay at the bottom of the tundish 1, so that this cooling water can be prevented from staying. In addition, it is preferable to control the supply amount of the cooling water or supply it intermittently instead of continuously. The water cooling apparatus 13 shown in FIG. 2 has a structure in which nozzle holes 13c (open holes) are provided at two locations of a water flow header 13a made of a steel pipe oriented in the horizontal direction, and cooling water is injected from the nozzle holes 13c. However, a water spray nozzle may be installed in place of the nozzle hole 13c, and cooling water may be sprayed from the water spray nozzle.

  By this water cooling, the surface temperature of the weir 6 in a portion within 100 mm from the joining position of the weir 6 and the irregular refractory 4 is lowered by 200 ° C. or more with respect to the surface temperature before the start of cooling. Thereafter, the weir 6 is lifted by using a lifting device such as a crane through a metal hanger 6 b installed at the upper end of the weir 6, and the weir 6 is removed from the tundish 1.

  The reason why the surface temperature of the weir 6 in a portion within 100 mm from the joining position of the weir 6 and the irregular refractory 4 by water cooling is lowered by 200 ° C. or more with respect to the surface temperature before the start of cooling is as follows. .

  After the primary cooling, the inventors perform water cooling of both ends of the weir 6 on the side where the weir 6 is joined to the amorphous refractory 4 from the state where the temperature of the weir 6 is 500 ° C. Then, the weir 6 is tundished 1 The test to remove from was performed. In the test, the ultimate surface temperature after water cooling of the weir 6 in a portion within 100 mm from the joining position was tested at four levels of 400 ° C., 350 ° C., 300 ° C., and 200 ° C.

  As a result, when the ultimate surface temperature is 400 ° C. and 350 ° C., the heat shrinkage at the end of the weir 6 is not sufficient, and the separation of the weir 6 from the irregular refractory 4 is difficult, and the weir 6 after recovery is damaged. However, the recovery rate of the reusable weir 6 was low. In contrast, when the ultimate surface temperature was 300 ° C. and 200 ° C., the reusable weir 6 could be recovered with high probability. This is because the thermal shrinkage of the weir 6 is larger than the thermal shrinkage of the irregular refractory 4, and the weir 6 and the irregular refractory 4 are separated, and the weir 6 can be easily removed from the tundish 1. Because it became.

  In the present invention, separation of the weir 6 and the irregular refractory 4 is promoted by thermal contraction of the weir 6, and the entire end portion of the weir 6 on the junction position side with the irregular refractory 4 is not cooled. It is essential to remove the weir 6 from the tundish 1 after the surface temperature has decreased by 200 ° C. or more. If the surface temperature of the weir 6 in this part is lowered by 200 ° C. or more with respect to the surface temperature before the start of cooling, the weir 6 and the amorphous refractory 4 are peeled off at that time, and once peeled, the heat is recovered. Even if the surface temperature of the weir 6 becomes less than 200 ° C. with respect to the surface temperature before the start of cooling, the weir 6 can be easily removed. Therefore, the weir 6 may be removed after reheating. However, from the viewpoint of heat shrinkage, it is desirable to remove the weir 6 when the temperature is lowered by 200 ° C. or more with respect to the surface temperature before the start of cooling.

  The shape of the weir 6 removed from the tundish 1 (chips, warpage, melting damage, cracks, etc.) is visually inspected, compared with the reuse conditions set in advance, and only the weir 6 that satisfies the reuse conditions is reused. . The reusable tundish of the weir 6 may be either the previous tundish or another tundish.

  As described above, according to the present invention, the surface of the weir 6 in a range within 100 mm from the joining position with the inner wall of the tundish is water-cooled, and the surface temperature of the weir 6 in this range is lowered by 200 ° C. or more. 6 is peeled from the inner wall of the tundish by heat shrinkage, and the weir 6 can be easily detached from the tundish 1. As a result, it is possible to collect the reusable weir 6 with a high probability without damaging the work refractory of the tundish 1 such as the irregular refractory 4.

  In the above description, the weir 6 is joined to the amorphous refractory 4. However, as disclosed in Patent Document 1, the coating layer having a thickness of 10 to 30 mm made of magnesia powder is applied to the amorphous refractory 4 by spraying or the like. 5 may be formed, and the coating layer 5 and the weir 6 may be joined. Moreover, although the said description is an example which applied this invention to the tundish 1 in which two 2-strand type weirs 6 were installed, the number of installation of the weirs 6 is not restricted to two, One or more The present invention can be applied to any tundish where the weir is installed.

  The tundish shown in FIG. 1 after being used in the continuous casting process of steel is first cooled by water spray until it reaches about 500 ° C., and then, as shown in FIG. The surface of the weir in the portion between the refractory and the portion within 100 mm from the bonding position was water cooled. The total supply flow rate of the cooling water from the two nozzle holes was 27 L / min.

The weir is a high alumina molded brick having a thickness of 100 mm, and its composition and physical property values are shown in Table 1. On the other hand, the amorphous refractory, which is a tundish work refractory, was constructed of an alumina-silica refractory high-alumina amorphous refractory containing 50% by mass or more of Al ₂ O ₃ .

  An example of measured values of the weir surface temperature during water cooling is shown in Table 2. In the test shown in Table 2, the injection of the cooling water from the water cooling device is not performed continuously, 5 minutes from the start of cooling to 5 minutes after the start of cooling, and 5 minutes from 16 minutes to 21 minutes later. For a total of 10 minutes. Water cooling is not performed during other periods. Parts 1 to 4 shown in Table 2 correspond to parts 1 to 4 shown in FIG. 2 and are the upper part and the lower part of both ends of the weir. Moreover, the weir surface temperature when the elapsed time shown in Table 2 is zero is the weir surface temperature just before the start of cooling.

  After 21 minutes from the start of cooling after an intermediate non-cooling period, a temperature drop exceeding 200 ° C. was obtained at each of the four temperature measuring points of the parts 1 to 4. In the test of Table 2, a non-cooling period is provided in the middle, but in the present invention, it is not essential to provide a non-cooling period, and the temperature may be lowered by 200 ° C. or more by one continuous cooling. In the test of Table 2, the surface temperature is measured without removing the weir even after the temperature drop exceeds 200 ° C. This is a test for confirming the transition of the surface temperature of the weir. by.

  With the surface temperature of the weir lowered by 200 ° C or more with respect to the surface temperature before the start of cooling, lift the weir by hooking the crane on the metal hanging hardware provided on the top of the weir and remove it from the tundish It was.

  The weirs removed from the tundish were compared with the weir reuse conditions shown in Table 3 to determine whether or not they can be reused, and only the weirs satisfying the reuse conditions were reused.

  In FIG. 3, when the weir is removed from the tundish by applying the present invention (example of the present invention), and after the entire tundish is cooled to about 400 to 500 ° C. by primary cooling, the weir is removed from the tundish (Comparative Example) shows the recovery rate of reusable weirs among the collected weirs. By applying the present invention, the recovery rate was improved by 6% (85 → 91%), and the cost of the weir refractory could be reduced.

DESCRIPTION OF SYMBOLS 1 Tundish 1A Molten steel injection | pouring part 1B Molten steel discharge | emission part 2 Iron skin 3 Permanent brick 4 Unfixed refractory 5 Coating layer 6 Weir 6a Dam hole 6b Hanging metal 7 Nozzle receiving brick 8 Top nozzle 9 Sliding nozzle 10 Fixed plate 11 Sliding Plate 12 Immersion nozzle 13 Water cooling device 13a Water flow header 13b Support base 13c Nozzle hole 14 Jet

Claims (2)

The tundish weir is removed from the used tundish, the removed weir is installed in the tundish again, and the tundish is used in the continuous casting process of molten steel,
The tundish after use is primarily cooled to reduce the surface temperature of the tundish work refractory and the weir to 400-600 ° C,
After that, using a water cooling device configured to supply cooling water to the end portion side of the weir tundish inner wall and the tundish inner wall, the joining position between the used tundish weir and the tundish inner wall and Water-cool the surface of the weir in the part up to 100mm from the joining position,
By this water cooling, the surface temperature of the weir in a portion within 100 mm from the joining position is reduced by 200 ° C. or more with respect to the temperature before the start of cooling,
Then, the method of reusing the tundish weir, characterized in that the weir is removed from the tundish.   2. The tundish weir according to claim 1, wherein a metal suspension is provided at an upper end of the weir, and the weir is lifted and removed from the tundish via the suspension. How to reuse.

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