Tundish apparatus and operation method using the same

Abstract

To provide a tundish device satisfactory in slag exhaust properties and further satisfactory in uniformity of the temperature and cleanliness of a molten steel made to outflow to each mold, and an operation method using the same.SOLUTION: According to a certain viewpoint in this invention, a tundish device used for steel continuous casting comprises: a diffusion part widen into a fan shape from an injection part of a molten steel; and an exhaust port formed at the terminal of the diffusion part and exhausting a molten steel to each mold. The diffusion part is formed with at least one step along the side wall of the diffusion part and is formed with an inclination part inclined from the terminal of the diffusion part toward a slag exhaust hole.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a tundish apparatus and an operating method using the same. [Background technology]

[0002] In continuous casting, as shown in Patent Documents 1 to 4, for example, molten steel stored in a ladle is first poured into a tundish and then poured into a mold. The tundish stabilizes the flow rate of molten steel poured into the mold, and, if there are multiple molds, distributes the molten steel to each mold. The tundish also has the function of removing inclusions in the molten steel by floating them up, thereby improving the cleanliness of the molten steel.

[0003] After a series of continuous castings is completed (i.e., after all the molten steel in the ladle has been continuously cast), the slag remaining in the tundish is removed, allowing the tundish to be reused. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 10-94860 [Patent Document 2] Japanese Patent Application Publication No. 10-71456 [Patent Document 3] Japanese Patent Application Publication No. 2017-177160 [Patent Document 4] Japanese Patent Application Laid-Open No. 2000-334549 Summary of the Invention [Problem to be solved by the invention]

[0005] If slag remains in the tundish after the slag has been removed, it may contaminate the next molten steel, resulting in a deterioration in the quality of the cast product. For this reason, for example, after several reuses, the amount of slag remaining may be small, and the quality of the product may meet the required standards, but subsequent products may not meet the required standards. Naturally, therefore, a tundish with poor slag removal performance will be reused less frequently. Therefore, the slag removal performance of a tundish has a significant impact on the quality of the product and operating costs.

[0006] On the other hand, continuous casting machines that produce small-cross-sectional area cast pieces such as bloom billets and round bloom billets require a large number of strands to ensure productivity. In such cases, the tundish equipment typically has three to six outlet holes for the molds. In such multi-strand tundish equipment, uniformity in the temperature and cleanliness of the molten steel flowing into each mold is also required.

[0007] The present invention has been made in view of the above problems, and an object of the present invention is to provide a tundish apparatus which has good slag removal properties and which also has good uniformity in the temperature and cleanliness of the molten steel flowing into each mold, and an operating method using the same. [Means for solving the problem]

[0008] In order to solve the above-mentioned problems, according to one aspect of the present invention, there is provided a tundish apparatus used in continuous casting of steel, comprising a diffusion section that spreads out in a fan shape from an injection section for molten steel, and a discharge port formed at the end of the diffusion section for discharging the molten steel into a mold, wherein the diffusion section has at least one step formed along its side wall, and an inclined section that slopes from the end of the diffusion section toward a slag discharge hole.

[0009] Here, the inclined portion may be provided at approximately the center in the width direction of the diffusion portion.

[0010] A weir may also be formed at the boundary between the injection section and the inclined section.

[0011] The slope may also be connected to the top end of the weir.

[0012] The height of the step formed at the lowest stage of the diffusion section may be 150 to 290 mm.

[0013] According to another aspect of the present invention, there is provided an operating method, characterized in that, when discharging the slag, the tundish apparatus described above is tilted by a predetermined angle and maintained at that angle for a predetermined time, thereby collecting the slag on the inclined portion, and then the tundish is tilted to the final angle, and the slag collected on the inclined portion is discharged through the slag discharge hole.

[0014] Here, the predetermined time may be 10 to 60 seconds, the predetermined angle may be 30 to 60°, and the tilting speed of the tundish device may be 1.2 to 2.4° / s. The final angle of the tundish tilting is 80 to 90°. [Effects of the Invention]

[0015] According to the above-described aspects of the present invention, it is possible to provide a tundish apparatus and an operating method using the same which have good slag removal properties and also have good uniformity in the temperature and cleanliness of the molten steel flowing into each mold. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a plan view schematically showing a conventional tundish device. [Figure 2] FIG. 2 is a cross-sectional view (side cross-sectional view) taken along line AA of the conventional tundish apparatus of FIG. [Figure 3] FIG. 1 is a side cross-sectional view schematically showing a first improved example of a tundish apparatus. [Figure 4] 4 is a side cross-sectional view schematically showing a second improved example of the tundish apparatus, in which only the side wall of the tundish apparatus is shown. [Figure 5] FIG. 1 is a plan view schematically showing a tundish apparatus according to an embodiment of the present invention. [Figure 6] FIG. 2 is a perspective view schematically showing a part of the tundish apparatus according to the present embodiment. [Figure 7] FIG. 6 is a cross-sectional view (side cross-sectional view) taken along the line AA in FIG. 5. [Figure 8] FIG. 10 is a side cross-sectional view showing a modified example of the weir. [Figure 9] 1 is a graph showing a comparison of inclusion outflow rates. [Figure 10] 1 is a graph showing a comparison of temperatures at the time of outflow of molten steel. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, the present embodiment will be described in detail with reference to the drawings. Note that a numerical range indicated using "to" includes the numerical values ​​on both ends of the "to".

[0018] <1. Overview of conventional tundish equipment> First, an overview of a conventional tundish apparatus 100 will be described with reference to Figures 1 and 2. Figure 1 is a plan view schematically showing the tundish apparatus 100, and Figure 2 is a side cross-sectional view (cross-sectional view along AA) schematically showing the tundish apparatus 100. The tundish apparatus 100 is a typical 6-strand tundish apparatus.

[0019] The tundish apparatus 100 includes a molten steel pouring section (pouring point) 101, a diffusion section 102 that spreads out in a fan shape from the molten steel pouring section 101, an end section 103 formed at the end of the diffusion section 102, and a discharge port 104 formed in the end section 103 for discharging the molten steel into a mold. Here, since the tundish apparatus 100 is for six strands, six discharge ports 104 are provided.

[0020] In such a tundish apparatus 100, molten steel is supplied from a ladle to a pouring section 101 of the tundish apparatus 100 through a pouring pipe 200 (or a long nozzle). Arrows 200a indicate the flow of molten steel poured into the pouring section 101. The molten steel supplied from the ladle to the tundish apparatus 100 flows through the diffusion section 102 to the end section 103, and is then supplied to a mold through a submerged nozzle 105 installed at a discharge port 104. A slag discharge hole 101b is provided in a side wall 101a of the pouring section 101, which is located on the opposite side of the pouring pipe 200 from the diffusion section 102.

[0021] The discharge ports 104 are counted from the right end as 1st (strand), 2nd, etc., and the distances from these discharge ports 104 to the pouring part 101 are compared. In this case, the distance from the 3rd and 4th strands, which are located in the center of the width of the tundish apparatus 100, to the pouring part 101 is the shortest. The temperature of the molten steel discharged from a discharge port 104 closer to the pouring part 101 tends to be higher than the temperature of the molten steel discharged from a discharge port 104 farther from the pouring part 101, and the cleanliness also tends to be worse.

[0022] Naturally, the temperature of the molten steel discharged from the discharge port 104 close to the injection part 101 is high (because the time it takes to reach the discharge port 104 is short), but the reason why the cleanliness of the molten steel deteriorates is because the time it takes for inclusions in the molten steel to float and separate (residence time in the tundish apparatus 100) is short. Therefore, one of the problems with the strand apparatus is that the temperature and cleanliness of the molten steel discharged from each discharge port 104 become uneven.

[0023] After the continuous casting process is completed (i.e., after all the molten steel in the ladle has been continuously cast), the slag remaining in the tundish apparatus 100 is drained. This allows the tundish apparatus 100 to be reused. At this time, as shown in FIG. 2, the tundish apparatus 100 is tilted around the rotation axis X to a final angle of 90° (clockwise in FIG. 2, i.e., the direction in which the slag drain hole 101b moves vertically downward; the horizontal direction is 0°). Here, the rotation axis X is an axis extending in the width direction of the tundish apparatus 100 (a direction perpendicular to the paper surface of FIG. 2). The rotation axis X is a distance L1 from the central axis 104a of the discharge port 104 (nozzle central axis) and a distance L2 from the bottom surface of the end portion 103. While the distances L1 and L2 can be set arbitrarily, for example, the distance L1 is approximately 450 mm, and the distance L2 is approximately 480 mm.

[0024] By tilting the tundish apparatus 100 in this manner, the slag in the tundish apparatus 100 flows toward the slag discharge hole 101b and is discharged from the slag discharge hole 101b. This allows the tundish apparatus 100 to be reused. However, as is clear from FIG. 2, the bottom surface 103a of the end portion 103 is designed to be lower than the bottom surface 102b of the diffusion section 102 by a distance L3. The distance L3 is arbitrary and may be, for example, approximately 230 mm. In other words, a step 110 is formed between the end portion 103 and the diffusion section 102. Therefore, even if the tundish apparatus 100 is tilted as described above, the slag gets caught on this step 110, making it difficult to sufficiently discharge the slag. Therefore, another problem with the tundish apparatus 100 is its poor slag discharge performance. For this reason, for example, after several reuses, the amount of slag remaining may be small and the quality of the finished product may meet the required standard, but the quality of the finished product thereafter may not meet the required standard.

[0025] <2. Investigation by the Inventor> In order to improve the slag discharge performance of the tundish apparatus 100, the inventors investigated eliminating the step 110 and sloping the bottom surface 102b of the diffusion section 102, as shown in FIG. 3. Note that FIG. 3 is a side cross-sectional view (corresponding to the AA cross-section in FIG. 1) that schematically shows a first improved example of the tundish apparatus 100. Simply eliminating the step 110 would cause the slag to come into contact with the upper part of the side wall 102a (see FIG. 1) of the diffusion section 102 when the tundish apparatus 100 was tilted as described above. In other words, this technique would cause another problem: the area contaminated by the slag would become wider.

[0026] Therefore, the inventors considered tilting the sidewall 102a of the diffusion section 102 by 0 to 10 degrees from the vertical direction, as shown in Figure 4. However, although this somewhat alleviated the problem of the slug contacting the upper part of the sidewall 102a of the diffusion section 102 (see Figure 1), it was not sufficient.

[0027] Furthermore, with regard to the angle β (see Figure 1) formed between the side wall 102a of the diffusion section 102 and the line connecting the central axis of the discharge port 104 (i.e., the width direction), Patent Document 2 states that if this angle β is set to 10° or more, the sludge removal performance will be good. However, when the inventors reproduced this technology, they found that sufficient effect could not be obtained.

[0028] Therefore, the present inventors have conducted extensive research into the configuration (shape) of a tundish apparatus that has good slag removal properties, does not expand the area contaminated by slag, and also ensures good uniformity in the temperature and cleanliness of the molten steel flowing into each mold. As a result, the inventors have come up with the tundish apparatus 10 described below. The tundish apparatus 10 according to this embodiment will be described below.

[0029] <3. Overall configuration of the tundish equipment> Next, the overall configuration of the tundish apparatus 10 according to this embodiment will be described with reference to Fig. 5 and Fig. 6. Here, Fig. 5 is a plan view schematically showing the tundish apparatus 10 according to this embodiment. Fig. 6 is a perspective view schematically showing a part of the tundish apparatus 10 according to this embodiment. More specifically, it is a perspective view showing one of two shapes obtained when the tundish apparatus 10 is cut along line AA.

[0030] The tundish apparatus 10 includes a molten steel pouring section (pouring point) 11, a diffusion section 12 that spreads out in a fan shape from the molten steel pouring section 11, an end section 13 formed at the end of the diffusion section 12, and a discharge port 14 formed at the end section 13 for discharging the molten steel into a mold. Here, since the tundish apparatus 10 is for six strands, six discharge ports 14 (1st to 6th st) are provided. There is no particular restriction on the number of strands, but considering that the diffusion section 12 has a diverging shape, it is preferable that there are three or more strands.

[0031] The configurations of the casting section 11 and the terminal section 13 are the same as those of the casting section 101 and the terminal section 103 described above. Of the side walls of the casting section 11, a side wall 11a located on the opposite side of the casting pipe 200 from the diffusion section 12 is provided with a slag discharge hole 11b (see FIGS. 7 and 8). As shown in FIG. 6, it is preferable that the bottom surface of the terminal section 13 be formed to have a uniformly flat shape so that molten steel does not concentrate at some of the discharge ports 14.

[0032] The diffusion section 12 has at least one step (one step in this example) formed along the side wall 12a of the diffusion section 12. That is, the diffusion section 12 has a lower step 12b and an upper step 12c, and the interface between them forms a step 12d. The step 12d is formed along the side wall 12a of the diffusion section 12. Note that, although the diffusion section 12 has one step in this embodiment, two or more steps may be formed to facilitate the installation of the refractory material and ensure its strength. The angle α formed between the step 12d and a line connecting the central axes of the discharge outlets 104 (i.e., the width direction of the diffusion section 12) is not particularly limited, and may be set arbitrarily within a range that achieves the effects of this embodiment. For example, the angle α may be approximately 10 to 15°. The angle β formed between the line connecting the central axes of the discharge outlets 104 (i.e., the width direction of the diffusion section 12) and the side wall 12a of the diffusion section 12 is not particularly limited, and may be set arbitrarily within a range that achieves the effects of this embodiment. As an example, the angle β may be approximately 20 to 25°. In the example shown in Fig. 6, the bottom surface 12c-1 of the upper section 12c is formed parallel to the bottom surface 12b-1 of the lower section 12b, but this is not limiting. For example, the bottom surface 12c-1 of the upper section 12c may be inclined with respect to the bottom surface 12b-1 of the lower section 12b so that the molten steel flowing onto the upper section 12c can easily flow down to the lower section 12b.

[0033] Furthermore, the height of the step 12d formed at the lowest stage of the diffusion section 12 is preferably 150 to 290 mm. In this case, it is possible to more reliably prevent the slag from contacting the side wall 12a of the diffusion section 12 during slag removal.

[0034] Furthermore, the diffusion section 12 is provided with an inclined section 12e that slopes from the end portion 13 of the diffusion section 12 toward the slag discharge hole 11b. The inclined section 12e is provided in the central portion (approximately the central portion) of the diffusion section 12 in the width direction. The weir 20 is provided at the boundary between the injection section 11 and the inclined section 12e. The size of the weir 20 is not particularly limited, and it may be designed appropriately so as to perform the function described below. For example, the height of the weir 20 may be approximately 130 mm, and the length (length in the direction from the injection section 11 toward the inclined section 12e) may be approximately 230 mm. By providing the weir 20, the molten steel supplied to the tundish apparatus 10 temporarily floats up. This causes inclusions to float up, improving the cleanliness of the molten steel. Details will be described later. Although the weir 20 does not necessarily have to be provided in the tundish apparatus 10, it is preferable to provide the weir 20 in the tundish apparatus 10 from the viewpoint of increasing the cleanliness of the molten steel. The inclined portion 12e does not necessarily have to be provided in the approximately central portion of the width direction of the diffusion section 12, but may be provided so that the slag is partially collected toward the slag discharge hole in the width direction of the diffusion section 12. The inclined portion 12e of this embodiment may be provided at an appropriate position that does not interfere with the collection of slag from the end portion 13 toward the slag discharge hole 11b (in the example shown in FIG. 6, from the vicinity of the step 12d to the position of the weir 20), and is not limited to the embodiment shown in FIG. 6. For example, the inclined portion 12e may be provided in a portion from a position closer to the discharge port 14 to the weir 20 than in the example shown in FIG. 6. In this case, the inclined portion 12e should have a gentle slope so that the collected slag does not stagnate along the step 12d. The inclination refers to a state in which the bottom surface of the inclined portion 12e is inclined at a certain angle or more relative to the bottom surface of the end portion 13. In the example of Fig. 6, the inclination is 15° relative to the horizontal plane, but it is not limited to 15°. The inclination angle is not a problem as long as it is within the range of angles that ensures slag removal and allows construction.

[0035] <4. Operation method using tundish equipment> Next, an operating method using the tundish apparatus 10 will be described with reference to Figures 5 to 7. Here, Figure 7 is a cross-sectional view (side cross-sectional view) taken along line AA in Figure 5. During continuous casting, molten steel is supplied from a ladle to the pouring section 11 of the tundish apparatus 10 through a pouring pipe 200 (or a long nozzle).

[0036] The molten steel supplied to the injection section 11 is first floated by the weir 20, as indicated by the arrow 200a. This allows inclusions to be more reliably floated. This improves the cleanliness of the molten steel discharged from each outlet 104. The molten steel then flows toward the end section 14. Here, a step 12d is formed in the diffusion section 12. This step 12d narrows the flow path toward the widthwise outer side of the diffusion section 12 (the flow path from the lower end of the inclined section 12e toward the widthwise outer end of the diffusion section 12). Therefore, the flow velocity of the molten steel flowing toward the widthwise outer side of the diffusion section 12 is faster than the flow velocity of the molten steel flowing through the center of the diffusion section 12. As a result, molten steel of a uniform quality (i.e., molten steel with a more uniform temperature and cleanliness) is supplied to the mold from each outlet 14. The uniformity of the temperature and cleanliness of the molten steel was confirmed by simulation. Details will be described later.

[0037] After the continuous casting process is completed (i.e., after all of the molten steel in the ladle has been continuously cast), the slag remaining in the tundish apparatus 10 is discharged. This allows the tundish apparatus 10 to be reused. At this time, the tundish apparatus 100 is tilted around an axis X', which is the same as the central axis of rotation X shown in FIG. 2, to a final angle of 80 to 90° (clockwise in FIG. 7, i.e., the direction in which the slag discharge hole 11b moves vertically downward; the horizontal direction is 0°). The tilting speed is not particularly limited, but may be, for example, approximately 1.2 to 2.4 seconds. In this embodiment, most of the slag flows along the arrow Y in FIG. 6 (i.e., along the step 12d and the inclined portion 12e) and is discharged from the slag discharge hole 11b. Therefore, the slag can be more reliably discharged while suppressing contamination of the side wall 12a of the inclined portion 12 (i.e., suppressing the extent of contamination by the slag). The slag removal performance was confirmed by numerical analysis simulation, the details of which will be described later.

[0038] However, since the weir 20 protrudes from the bottom surface of the injection section 11, there is a possibility that the slag may get caught on the weir 20 during slag discharge. Therefore, as shown in FIG. 8, the inclined portion 12e may be connected to the upper end of the weir 20. In other words, the weir 20 may have a sloped shape. In this case, the slag can easily climb over the weir 20 during slag discharge, making it possible to discharge the slag more reliably. Note that FIG. 8 is a cross-sectional view taken from the same perspective as FIG. 7.

[0039] Furthermore, before tilting the tundish apparatus 10 to the final angle (90°), the tundish apparatus 10 may be tilted by a predetermined angle and maintained for a predetermined time, thereby allowing the slag to collect on the inclined portion 12e. Then, by tilting the tundish apparatus 10 to the final angle (90°), the slag can be more reliably removed. The predetermined time and predetermined angle can be adjusted appropriately depending on the actual tundish apparatus 10. For example, the predetermined time may be 10 to 60 seconds, and the predetermined angle may be 30 to 60°. In this case, the slag can be more reliably removed.

[0040] <5. Comparison by simulation> Next, a comparison based on numerical analysis fluid simulation will be described. The numerical analysis fluid simulation was performed according to the method described in "K. Takatani, ISIJ International, Vol. 43, 2003, No. 6, pp. 915-922."

[0041] As tundish apparatuses, a conventional tundish apparatus 100 (corresponding to the configuration shown in FIG. 2) and tundish apparatuses 10 and 10' according to this embodiment were used. Here, the tundish apparatus 10 has a weir 20 (corresponding to the configuration shown in FIG. 7), and the tundish apparatus 10' does not have a weir 20 (corresponding to the configuration without the weir 20 in FIG. 7). Both tundish apparatuses were for six-strand use. The angle β between the side wall 102a of the diffusion section 102 of the tundish apparatus 100 (or the side wall 12a of the diffusion section 12) and the width direction of the tundish apparatus 100 (or the tundish apparatus 10 and 10') was 23°, and the angle α between the step 12d of the diffusion section 12 and the width direction of the tundish apparatus 10 was 12°. The height of the step 12d was 150 mm. The shape of the weir 20 was as shown in Fig. 7, and the height of the weir 20 was 130 mm and the length was 230 mm. Other conditions were the same for the tundish apparatuses 10, 10', and 100.

[0042] Furthermore, the problem with steel products is inclusions with a diameter of 30 μm or more, especially 50 μm or more, which are mainly composed of alumina. In this numerical analysis fluid simulation, 3 It was assumed that particles with diameters of 30, 50, and 100 μm were contained in the molten steel as inclusions. 3 It was assumed that the molten steel flowed into the tundish at a concentration of 100 tons / min. The total amount of molten steel discharged from the six discharge ports 104 (strands) was 5 tons / min. A numerical analysis fluid simulation was performed under these conditions.

[0043] FIG. 9 shows the results of evaluating the ratio of the inclusion concentration flowing into the tundish apparatus 10, 10', and 100 to the inclusion concentration (average concentration over six strands) flowing into the mold. The lower this ratio, the higher the cleanliness of the molten steel flowing into the mold. For all particle sizes, the tundish apparatus 10 with the weir 20 had the highest cleanliness, and the tundish apparatus 10' without the weir 20 had the second highest cleanliness. In particular, when the particle size increased to 50 μm and 100 μm, the difference was significant. Therefore, according to this embodiment, molten steel with high cleanliness can be supplied to the mold.

[0044] The reason why the cleanliness of the molten steel is high even in the tundish apparatus 10' that does not have the weir 20 is that the tundish apparatus 10' has a sloped portion on its bottom surface, which increases the volume and lengthens the residence time of the molten steel compared to the conventional tundish apparatus 100. In addition, the bottom surface of the tundish apparatus 10' is more complex than that of the conventional tundish apparatus 100, with the step 12d and sloped portion 12e, which act as a weir and are thought to promote the floating of the molten steel.

[0045] Next, the temperature of the molten steel discharged from each outlet 104 (or 14) was evaluated by numerical analysis simulation. The results are shown in Figure 10. The outlet temperature, shown on the vertical axis, is the difference (latter - former) between the temperature of the molten steel when it was supplied to the tundish apparatus and the temperature of the molten steel discharged from each outlet 104 (or 14). It can be said that the more uniform this temperature distribution, the higher the quality of the finished product. As shown in Figure 10, in the conventional tundish apparatus 100, there is a large difference in the amount of temperature drop of the molten steel between the outlets 104 (1st, 6th) far from the pouring section 101 and the outlets 104 (3rd, 4th) close to the pouring section 101. However, in the tundish apparatus 10, 10' according to this embodiment, the temperature distribution of the molten steel discharged from each outlet 14 is more uniform. This is because the molten steel reaches the outlet 14 far from the pouring section 11 more quickly. This effect is particularly noticeable in the tundish apparatus 10 having the weir 20. This is because the molten steel rises to the surface and is stirred by the weir 20, so that the temperature of the molten steel supplied to each discharge port 14 becomes more uniform.

[0046] Although the distribution of inclusions is not shown here, the longer the time (residence time) it takes for the molten steel to reach the discharge port 14 from the pouring part 11, the more the cleanliness of the inclusions improves, resulting in a distribution similar to the temperature distribution. That is, in the conventional tundish apparatus 100, it is estimated that the amount of inclusions is greater at the discharge ports 104 (3rd and 4th ports) closer to the pouring part 104 and less at the discharge ports 104 (1st, 2nd, 5th, and 6th ports) farther from the pouring part. In contrast, in the tundish apparatus 10, 10' according to the present embodiment, the molten steel reaches the discharge ports 104 farther from the pouring part 11 more quickly, so there is almost no difference in the time it takes for the molten steel to reach the discharge ports 14 (1st and 6th ports) farther from the pouring part 11 and the discharge ports 14 (3rd and 4th ports) closer to the pouring part 11. It is estimated that this results in a more uniform cleanliness of the molten steel discharged from each discharge port 14.

[0047] As described above, the tundish apparatus 10 according to this embodiment provides good slag removal performance, and also provides good uniformity in the temperature and cleanliness of the molten steel flowing into each mold. [Example]

[0048] Next, examples of this embodiment will be described. In these examples, operations (particularly slag removal) were performed using several types of tundish apparatuses, and the results were evaluated. All tundish apparatuses used were six-strand tundish apparatuses. The angle β between the side wall of the diffusion section of the tundish apparatus and the width direction of the tundish apparatus was set to the value shown in Table 1, and the angle α between the step of the diffusion section and the width direction of the tundish apparatus was also set to the value shown in Table 1. The height of the step (lower step height) was also set to the value shown in Table 1. The height of the weir was 130 mm and the length was 230 mm. In Table 1, weir shape category A shows the shape shown in Figure 7, and category B shows the shape shown in Figure 8. Other conditions were the same as those used in a general tundish apparatus and were common to all levels.

[0049] [Table 1]

[0050] At each level, continuous casting of low-carbon steel was carried out using a tundish. The amount of molten steel was 5 tons / min. After continuous casting was completed, slag removal was performed. Specifically, the tundish was tilted at the tilting speed shown in Table 1. The tilting direction was set so that the slag removal hole faced downward. For levels with a set "holding angle," the tundish was held at that "holding angle" for the "holding time," and then tilted to the "final angle." The holding angle and final angle are angles with the tilting direction as the positive direction, with the horizontal direction being 0°. The "slag removal time" is calculated as (final angle) / (tilting speed) + (holding time).

[0051] Level 1 is an example in which a conventional tundish was used with a conventional slag removal method. In Level 1, the remaining slag amount was high at 186 kg, and much of the slag remained attached to the side walls of the diffusion section of the tundish. In terms of slag removal performance, a small amount of slag remaining and a short slag removal time are desirable. The less slag adhered to the side walls of the diffusion section, the shorter the maintenance time when reused and the less contamination of molten steel when reused. In this example, a slag remaining amount of 150 kg or less and an amount of adhesion to the side walls of the diffusion section, which was judged visually, were deemed acceptable if they were "medium" or less.

[0052] Level 2 is an example using the tundish apparatus according to this embodiment. However, the holding time and holding angle were not set. In Level 2, the amount of slag remaining was reduced to an acceptable level, and the amount of slag adhering to the side wall was also improved compared to Level 1. However, the effect was lower than in the other levels.

[0053] Level 3 is an example in which the tundish equipment according to this embodiment was used and the holding time and holding angle were set. According to Level 3, the amount of slag remaining was significantly reduced to 38 kg, and the amount of slag adhering to the side wall was also "small." Subsequently, several tests were conducted based on Level 3.

[0054] Levels 4 to 6 are examples where the tilting speed was changed. When the tilting speed was reduced to 1.2° / s as in level 4, the amount of remaining slag decreased slightly, but the slag draining time became longer at 96 s. Levels 5 and 6 are examples where the tilting speed was increased to 2.0 and 2.4° / s, respectively, and the slag draining time became shorter, but the amount of remaining slag increased. In level 6, some of the slag overflowed the lower level, resulting in increased adhesion to the side walls. Therefore, the preferred range for the tundish tilting speed is 1.2 to 2.4° / s, and a range of 1.2 to 2.0° / s is desirable.

[0055] Levels 7 to 11 are examples where the holding time was varied. The amount of remaining slag increased as the holding time was shortened, and in level 9, where the holding time was shortened to 10 s, the amount of remaining slag increased to 48 kg. Levels 10 and 11 are examples where the holding time was lengthened. In level 10, where the holding time was extended by 15 s from level 3, the amount of remaining slag decreased, but in level 11, where the holding time was extended by 30 s from level 3, the amount of remaining slag increased. This is thought to be due to the slag cooling and becoming more likely to solidify. Therefore, a holding time of 10 to 60 s is preferable, with a range of 20 to 45 s being more preferable.

[0056] Levels 12 to 17 are examples in which the lower tier height (height of step 12d) was changed. The lower the lower tier height, the easier it was for the slag to pass over the lower tier before gathering in the center during tilting. Therefore, the higher the lower tier height, the less slag remained. However, even if the lower tier height exceeds 290 mm, the effect is small. Therefore, the lower tier height is preferably 150 to 320 mm, and more preferably 150 to 290 mm.

[0057] Levels 18 and 19 are examples where the effect of tilt speed was confirmed when the lower stage height was 150 mm, and there was no problem within the tilt speed range of 1.2 to 2.0° / s.

[0058] Levels 20 and 21 are cases where the effect of tilt speed was confirmed when the lower stage height was set to 290 mm, and good results were obtained without any problems within the tilt speed range of 1.2 to 2.0° / s.

[0059] Levels 22 to 24 are the results of checking the influence of the holding angle, and there was no significant difference in the range of 30 to 60 degrees. However, the results were good.

[0060] Levels 25 to 28 are examples in which the angles α and β were changed from α = 12° and β = 23° in the base (Level 3). As a result, in the range of α = 10 to 15° and β = 20 to 25°, there was no significant change in the amount of slag remaining, and there was little adhesion to the side wall of the diffusion section.

[0061] Level 29 is a case where tilting was stopped midway in a conventional tundish, as in level 3. The amount of slag stagnating in the tundish increased, and no improvement in slag removal was observed.

[0062] Level 30 is the case where the weir is rectangular A under the same conditions as level 3. As a result, the amount of slag remaining was about 10% more than with the slope type, but it was confirmed that this is not a problem in practical use.

[0063] Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to these examples. It is clear that a person skilled in the art to which the present invention pertains can conceive of various modifications and alterations within the scope of the technical ideas set forth in the claims, and it is understood that these also naturally fall within the technical scope of the present invention. [Explanation of symbols]

[0064] 10 Tundish equipment 11 Injection part 12 Diffusion section 12a Side wall of the diffusion section 12b Lower section 12c upper section 12d step 13 End 14 Outlet 20 Weir

Claims

1. A tundish apparatus used in continuous casting of steel, comprising: A diffusion area that spreads out like a fan from the injection area of ​​molten steel, a plurality of discharge ports formed at an end portion of the diffusion section for discharging the molten steel into a mold, The diffusion section has at least one step formed along a side wall of the diffusion section, and an inclined portion inclined from an end portion of the diffusion section toward a slag discharge hole, A tundish apparatus, characterized in that a weir is formed at a boundary between the pouring portion and the inclined portion.

2. 2. The tundish apparatus according to claim 1, wherein the inclined portion is provided at a central portion in the width direction of the diffusion portion.

3. 3. The tundish apparatus according to claim 1, wherein the inclined portion is connected to an upper end of the weir.

4. 4. The tundish apparatus according to claim 1, wherein the height of the step formed at the lowest stage of the diffusion section is 150 to 290 mm.

5. An operating method characterized by the fact that, when discharging slag, the tundish apparatus according to any one of claims 1 to 4 is tilted by a predetermined angle and maintained at that angle for a predetermined time, thereby allowing the slag to collect on the inclined portion, and then the tundish apparatus is tilted to a final angle, and the slag collected on the inclined portion is discharged from the slag discharge hole.

6. 6. The operating method according to claim 5, wherein the predetermined time is 10 to 60 seconds, the predetermined angle is 30 to 60°, and the tilting speed of the tundish apparatus is 1.2 to 2.4° / s.

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