Long nozzle and method for manufacturing cast piece

Abstract

To provide a long nozzle capable of effectively suppressing the intrusion of air.SOLUTION: The long nozzle 10 is a long nozzle connected to a lower nozzle 221 of a molten steel discharging device of a molten steel ladle, and has a slit 10b for injecting gas toward the lower nozzle 221 from the outside in the radial direction of the lower nozzle 221, wherein the width b of the slit 10b is 0.5 mm or more and 2.0 mm or less, and the slit 10b has a structure in which deformation due to thermal expansion is suppressed.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a long nozzle and a method for manufacturing a cast piece. [Background technology]

[0002] In a continuous casting machine, molten steel is poured from a ladle into a tundish using a nozzle called a long nozzle.

[0003] Japanese Patent Application Laid-Open Publication No. 2011-212721 discloses a long nozzle equipped with a metal case, which has a first gas outlet for ejecting inert gas between the metal case and the refractory material of the nozzle body, and a plurality of second gas outlets on the upper end surface of the metal case.

[0004] Japanese Patent Laid-Open Publication No. 5-31556 discloses a continuous casting nozzle in which an airtight fitting portion at the upper end with a nozzle positioned above is constituted by a lower fitting tapered surface and an upper spherical surface. In this continuous casting nozzle, the lower fitting tapered surface is an airtight fitting surface with an effective fitting rate of 65% between it and the lower fitting surface of the nozzle positioned above, and the upper spherical surface is an airtight fitting auxiliary spherical surface.

[0005] Japanese Patent Application Laid-Open No. 8-19855 discloses a nozzle for injecting molten metal that is connected to a lower nozzle for outflowing molten steel. This nozzle has a gas flow path that connects an inert gas outlet with a gas pressure equalizing chamber inside the nozzle.

[0006] Japanese Patent Application Laid-Open Publication No. 2001-212656 discloses a molten metal treatment apparatus having a vessel for containing molten metal, a flow rate control device for molten metal attached to the bottom of the vessel, a refractory provided below the flow rate control device, and an immersion nozzle provided below the refractory, with the joint surface of the refractory and the joint surface of the immersion nozzle joined together. In this apparatus, an annular slit is formed along the outer periphery of the immersion nozzle, with an opening at the joint surface of the immersion nozzle, and the opening of the slit is closed by a fireproof sheet. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-212721 [Patent Document 2] Japanese Patent Application Publication No. 5-31556 [Patent Document 3] Japanese Patent Application Publication No. 8-19855 [Patent Document 4] Japanese Patent Application Laid-Open No. 2001-212656 Summary of the Invention [Problem to be solved by the invention]

[0008] In a continuous casting machine, the ladle may be replaced during operation, and therefore the long nozzle preferably has a structure that allows connection to the bottom nozzle of the molten steel discharge device of the ladle (hereinafter simply referred to as the "bottom nozzle") in a short time and that effectively prevents air from entering.

[0009] As described in the above Patent Documents 1 to 4, a purge gas is injected into the fitting portion between the lower nozzle and the long nozzle to prevent air from entering the long nozzle from the fitting portion. However, depending on the structure of the fitting portion, increasing the flow rate of the purge gas may not be enough to prevent air from entering the long nozzle.

[0010] An object of the present invention is to provide a long nozzle that can effectively suppress the intrusion of air. Another object of the present invention is to provide a method for producing a cast slab with few impurities. [Means for solving the problem]

[0011] A long nozzle according to one embodiment of the present invention is a long nozzle connected to a lower nozzle of a molten steel discharge device of a molten steel ladle, and has a slit for injecting gas from the radial outside of the lower nozzle toward the lower nozzle, the width b of the slit being 0.5 mm or more and 2.0 mm or less, and the slit having a structure that suppresses deformation due to thermal expansion.

[0012] A method for producing a slab according to one embodiment of the present invention includes a step of producing a slab using a continuous casting apparatus including the above-described long nozzle. [Effects of the Invention]

[0013] According to the present invention, it is possible to effectively suppress the intrusion of air into the long nozzle, and also to produce a cast slab with fewer impurities. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a cross-sectional view schematically showing the configuration of a main part of a continuous casting device including a long nozzle according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view schematically showing the configuration of the connecting portion between the long nozzle and the bottom nozzle according to the first embodiment of the present invention. [Figure 3] FIG. 3 is a partial cross-sectional view of a long nozzle according to a first embodiment of the present invention. [Figure 4] FIG. 4 is an enlarged cross-sectional view showing a connecting portion between a long nozzle and a bottom nozzle according to the first embodiment of the present invention. [Figure 5] FIG. 5 is a diagram schematically illustrating the configuration of a long nozzle according to a second embodiment of the present invention. [Figure 6] FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. [Figure 7] FIG. 7 is a diagram schematically showing the configuration of a long nozzle according to a third embodiment of the present invention. [Figure 8] FIG. 8 is a cross-sectional view taken along line VIII-VIII in FIG. [Figure 9] Figure 9 is a block diagram of the test equipment used in the laboratory tests. [Figure 10] FIG. 10 is a schematic diagram of the test equipment used in the laboratory tests. [Figure 11] FIG. 11 is a graph showing the relationship between the width b of the slit and the amount of suction air. [Figure 12] FIG. 12 is a graph showing the amount of nitrogen absorption in the examples and comparative examples. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals, and the description thereof will not be repeated. The dimensional ratios between the components shown in each drawing do not necessarily represent the actual dimensional ratios.

[0016] [First embodiment] 1 is a cross-sectional view schematically showing the configuration of a main part of a continuous casting apparatus 1 including a long nozzle 10 according to a first embodiment of the present invention. The continuous casting apparatus 1 includes a molten steel ladle 21, a molten steel discharge device (e.g., a sliding nozzle device) 22, the long nozzle 10, a tundish 23, a submerged nozzle 24, and a mold 25.

[0017] In the continuous casting apparatus 1, molten steel is first poured from the ladle 21 into the tundish 23, and then poured from the tundish 23 into the mold 25. The molten steel is poured from the ladle 21 into the tundish 23 using a long nozzle 10, and from the tundish 23 into the mold 25 using a submerged nozzle 24, both in a state where the molten steel is shielded from air. The long nozzle 10 is connected to a bottom nozzle 221 of a molten steel discharge device 22 for the molten steel ladle 21.

[0018] 2 is a cross-sectional view schematically showing the configuration of the connection portion between the long nozzle 10 and the lower nozzle 221. FIG. 3 is a partial cross-sectional view of the long nozzle 10. The long nozzle 10 includes a nozzle body 11, a case 12, and a gas introduction pipe 13.

[0019] The nozzle body 11 is made of a refractory material and has a generally cylindrical shape, and a recess 11a is formed at the upper end of the nozzle body 11 for fitting the lower nozzle 221 therein.

[0020] The case 12 is made of metal and is formed to cover the outer periphery of the nozzle body 11 and part of the upper end 111. An opening 12a for inserting the lower nozzle 221 is formed at the upper end of the case 12.

[0021] A gap of a predetermined size is provided over the entire circumferential direction between the outer circumferential surface of nozzle body 11 and the inner circumferential surface of case 12, and this gap forms a pressure equalizing chamber 10a on the radially outer side of nozzle body 11. In addition, a gap of a predetermined size is provided between upper end 111 of nozzle body 11 and case 12, and this gap forms a slit 10b over the entire circumferential direction that continues from pressure equalizing chamber 10a to the space on the lower nozzle 221 side.

[0022] The gas inlet pipe 13 is formed so as to be able to introduce gas into the pressure equalizing chamber 10a. By introducing gas into the pressure equalizing chamber 10a from the gas inlet pipe 13, the gas is injected from the entire circumferential direction, through the slits 10b, and from the radially outer side of the lower nozzle 221 toward the lower nozzle 221.

[0023] 3, arrows schematically indicate the flow of gas introduced from gas introduction pipe 13. It is preferable that long nozzle 10 has a structure that allows gas to be sprayed horizontally toward lower nozzle 221. For this reason, slit 10b is preferably formed parallel to a horizontal plane (a plane perpendicular to the axial direction of long nozzle 10).

[0024] As described above, in this embodiment, slit 10b is defined by upper end 111 of nozzle body 11 and case 12. The lower surface of portion 121 of case 12 adjacent to slit 10b and the upper surface of upper end 111 of nozzle body 11 are parallel to each other. As described above, slit 10b is preferably formed parallel to the horizontal plane. That is, the lower surface of portion 121 of case 12 adjacent to slit 10b and the upper surface of upper end 111 of nozzle body 11 are preferably formed parallel to the horizontal plane. More specifically, the angles formed between these surfaces and the horizontal plane are preferably within ±10°, and more preferably within ±5°.

[0025] The bottom nozzle 221 is fitted into the recess 11a of the nozzle body 11. The bottom nozzle 221 is pressed against the nozzle body 11 with, for example, a predetermined load so that the bottom nozzle 221 and the nozzle body 11 are in close contact with each other. However, due to unevenness on the surfaces of the bottom nozzle 221 and the nozzle body 11, a small gap may be formed between the bottom nozzle 221 and the nozzle body 11. Furthermore, a molten steel flow is generated inside the bottom nozzle 221 and the nozzle body 11. This molten steel flow may cause air to be sucked in from the fitting portion between the bottom nozzle 221 and the nozzle body 11.

[0026] In this embodiment, a purge gas (e.g., Ar gas) is injected from the slit 10b toward the lower nozzle 221. The flow rate of the injected purge gas is not particularly limited, but is, for example, 50 to 1000 NL / min, and preferably 100 to 500 NL / min. This prevents air from entering the long nozzle 10 from the mating portion between the lower nozzle 221 and the nozzle body 11. However, depending on the structure of the mating portion, increasing the flow rate of the purge gas may not sufficiently prevent air from entering the long nozzle 10.

[0027] 4 is an enlarged cross-sectional view showing the connection portion between the long nozzle 10 and the lower nozzle 221. In this embodiment, the width b of the slit 10b is 0.5 mm or more and 2.0 mm or less, and the slit 10b has a structure that suppresses deformation due to thermal expansion.

[0028] Slit Width In the long nozzle 10 according to this embodiment, the width b of the slit 10b is 0.5 mm or more and 2.0 mm or less. By setting the width b of the slit 10b to 0.5 mm or more and 2.0 mm or less, it is possible to efficiently prevent air from entering the long nozzle 10. More specifically, the width b of the slit 10b in this embodiment is the distance between the lower surface of the portion 121 of the case 12 adjacent to the slit 10b and the upper surface of the upper end portion 111 of the nozzle body 11.

[0029] The wider the width b of the slit 10b, the wider the jet width of the purge gas. Air entrained from the upper part of the jet diffuses within the jet and penetrates the mating portion between the lower nozzle 221 and the nozzle body 11. Increasing the width of the purge gas jet reduces the amount of air reaching the mating portion. On the other hand, if the width b of the slit 10b is too large, uniform purging in the circumferential direction becomes difficult. As described above, in this embodiment, the purge gas is injected from the entire circumferential direction, from the radially outer side of the lower nozzle 221 toward the lower nozzle 221. Injecting the purge gas from the entire circumferential direction shields the mating portion from air by a "surface," achieving high purging efficiency. If the width b of the slit 10b is too large, the injection amount from the side closer to the gas inlet pipe 13 increases and the injection amount from the diagonal direction decreases, resulting in reduced purging efficiency.

[0030] The lower limit of the width b of the slit 10b is preferably 0.8 mm, and the upper limit of the width b of the slit 10b is preferably 1.6 mm.

[0031] [Suppression of deformation due to thermal expansion] The long nozzle 10 according to this embodiment has a structure in which the slit 10b is prevented from being deformed due to thermal expansion.

[0032] Typically, the slit of a long nozzle is made of dissimilar materials, with the upper part made of general structural steel such as SS400 and the lower part made of refractory. The metal case and refractory are bonded to the side of the long nozzle with mortar or other adhesive, but the slit part is not fixed and is easily deformed. As a result, when molten steel is poured, a temperature distribution occurs, and the metal case may deform due to thermal expansion. If the metal case deforms during operation, the slit width changes, making it impossible to maintain the appropriate slit width described above.

[0033] In this embodiment, as a specific structure for suppressing deformation due to thermal expansion, the thickness of the upper part of the slit 10b is made thicker than usual. More specifically, the thickness t of the portion 121 of the case 12 adjacent to the slit 10b is made 4.0 mm or more. By increasing the thickness t, the rigidity of the portion 121 of the case 12 adjacent to the slit 10b is improved, and it is possible to suppress changes in the width b of the slit 10b during operation. The lower limit of the thickness t is preferably 4.2 mm. The upper limit of the thickness t is not particularly limited, but is, for example, 10.0 mm, and preferably 8.0 mm.

[0034] 4 illustrates a case where the thickness t of a portion 121 of the case 12 adjacent to the slit 10b is thicker than the thickness of other portions of the case 12. This configuration is an example, and the entire thickness of the case 12 may be 4.0 mm or more.

[0035] The long nozzle 10 according to the first embodiment of the present invention has been described above. The long nozzle 10 according to this embodiment can effectively prevent air from entering the long nozzle 10. Therefore, by producing a cast slab using a continuous casting apparatus 1 including the long nozzle 10, a cast slab with reduced impurities such as nitrogen can be produced.

[0036] In the above description, the case 12 covers the outer periphery and part of the upper end 111 of the nozzle body 11, but this configuration is an example. It is sufficient that the case 12 covers part of the upper end 111 of the nozzle body 11.

[0037] [Second embodiment] Fig. 5 is a diagram schematically illustrating the configuration of a long nozzle 30 according to a second embodiment of the present invention. More specifically, Fig. 5 is an enlarged cross-sectional view illustrating the connection portion between the long nozzle 30 and the lower nozzle 221.

[0038] The long nozzle 30 differs from the long nozzle 10 (FIG. 4) according to the first embodiment in the structure near the slit. The long nozzle 30 has a slit 30b instead of the slit 10b (FIG. 4) of the long nozzle 10.

[0039] In addition to the nozzle body 11 and the case 12, the long nozzle 30 further includes a metal member 322 disposed between the upper end portion 111 of the nozzle body 11 and the case 12. In this embodiment, the slit 30b is formed by the metal member 322 and the case 12. The lower surface of a portion 321 of the case 12 adjacent to the slit 30b and the upper surface of the metal member 322 are parallel to each other. The angle between these surfaces and the horizontal plane is preferably within ±10°, and more preferably within ±5°.

[0040] In this embodiment, as in the case of the long nozzle 10 (FIG. 4), the width b of the slit 30b is 0.5 mm or more and 2.0 mm or less. More specifically, the width b of the slit 30b in this embodiment is the distance between the lower surface of the portion 321 of the case 12 adjacent to the slit 30b and the upper surface of the metal member 322.

[0041] In the long nozzle 10 (FIG. 4), the thickness t of the upper portion of the slit 10b (portion 121 of the case 12 adjacent to the slit 10b) is increased to suppress deformation of the slit 10b due to thermal expansion. Instead, in this embodiment, the upper and lower portions of the slit 30b are both made of metal, more specifically, the slit 30b is formed of a metal member 322 and the case 12, thereby suppressing deformation of the slit 30b due to thermal expansion. In other words, by forming the upper and lower portions of the slit 30b from the same material (metal), the difference in thermal expansion between the two portions is reduced, suppressing change in the width b of the slit 30b during operation.

[0042] In this embodiment, the thickness of the metal member 322 and the case 12 is arbitrary. However, to further increase rigidity, the thickness of one or both of them may be 4.0 mm or more.

[0043] The metal constituting member 322 may be a different type of metal from the metal constituting case 12, but is preferably the same type of metal.

[0044] The metal member 322 is preferably fixed to the case 12. Specifically, for example, as shown in Fig. 5, the metal member 322 is extended to a portion of the case 12 that is closer to the outer periphery than the nozzle body 11, and the metal member 322 is fixed to this portion. The metal member 322 and the case 12 are preferably fixed by welding. This makes it possible to make the slit 30b less likely to deform.

[0045] Furthermore, in this embodiment, a spacer 323 having a thickness substantially equal to the width b of the slit 30b is disposed between the metal member 322 and a portion 321 of the case 12 adjacent to the slit 30b. The spacer 323 is made of, for example, metal. The spacer 323 is fixed (preferably welded) to both the portion 321 of the case 12 adjacent to the slit 30b and the metal member 322. This makes it possible to make the slit 30b less likely to deform.

[0046] Figure 6 is a cross-sectional view taken along line VI-VI in Figure 5. More specifically, Figure 6 is a cross-section of the long nozzle 30 taken along a plane perpendicular to the axial direction of the long nozzle 30 and passing through the center of the width direction of the slit 30b (the axial direction of the long nozzle 30). It is preferable that the circumferential width c of the spacer 323 be small so as not to impair the circumferential uniformity of the jet. The circumferential width c of the spacer 323 is preferably 5 mm or less (approximately the width of a welding point).

[0047] The spacers 323 are preferably arranged at two or more locations in the circumferential direction of the slit 30b. The number of spacers 323 is not limited to this, but is, for example, 2 to 8. When the spacers 323 are arranged at multiple locations in the circumferential direction of the slit 30b, they are preferably arranged at equal intervals.

[0048] 5, the metal member 322 is fixed to the case 12 on both radial sides of the long nozzle 30. That is, one end is fixed to a portion of the case 12 that is closer to the outer periphery than the nozzle body 11, and the other end is fixed via a spacer 323 to a portion 321 of the case 12 that is adjacent to the slit 30b. This configuration makes the slit 30b less likely to deform.

[0049] The long nozzle 30 according to the second embodiment of the present invention has been described above. This embodiment also makes it possible to effectively prevent air from entering the long nozzle 30.

[0050] [Third embodiment] 7 is a diagram schematically illustrating the configuration of a long nozzle 40 according to a third embodiment of the present invention. More specifically, FIG. 7 is an enlarged cross-sectional view illustrating the connection portion between the long nozzle 40 and the lower nozzle 221.

[0051] The long nozzle 40 differs from the long nozzle 10 (FIG. 4) according to the first embodiment in the structure near the slit. The long nozzle 40 has a slit 40b instead of the slit 10b (FIG. 4) of the long nozzle 10.

[0052] In addition to the nozzle body 11 and the case 12, the long nozzle 40 further includes a refractory member 112 arranged above the nozzle body 11. More specifically, the refractory member 112 is arranged between the upper end portion 111 of the nozzle body 11 and the case 12. In this embodiment, the slit 40b is formed by the upper end portion 111 of the nozzle body 11 and the refractory member 112. The lower surface of the refractory member 112 and the upper surface of the upper end portion 111 of the nozzle body 11 are parallel to each other. The angle formed by these surfaces and the horizontal plane is preferably within ±10°, and more preferably within ±5°.

[0053] In this embodiment, as in the case of the long nozzle 10 (FIG. 4), the width b of the slit 40b is 0.5 mm or more and 2.0 mm or less. More specifically, the width b of the slit 40b in this embodiment is the distance between the lower surface of the refractory member 112 and the upper surface of the upper end portion 111 of the nozzle body 11.

[0054] In the long nozzle 10 (FIG. 4), the thickness t of the upper portion of the slit 10b (portion 121 of the case 12 adjacent to the slit 10b) is increased to suppress deformation of the slit 10b due to thermal expansion. Instead, in this embodiment, both the upper and lower portions of the slit 40b are made of refractory materials, more specifically, the slit 40b is formed by an upper end portion 111 of the nozzle body 11 and a refractory member 112, thereby suppressing deformation of the slit 40b due to thermal expansion. In other words, by forming the upper and lower portions of the slit 40b from the same material (refractory), the difference in thermal expansion between the upper and lower portions is reduced, suppressing change in the width b of the slit 40b during operation.

[0055] The thickness of the refractory member 112 is arbitrary, but in order to further increase rigidity, the thickness of the refractory member 112 may be 4.0 mm or more.

[0056] The refractory material constituting the member 112 may be of a different type from the refractory material constituting the nozzle body 11, but is preferably of the same type.

[0057] Fig. 8 is a cross-sectional view taken along line VIII-VIII in Fig. 7. As shown in Fig. 8, the refractory member 112 and the nozzle body 11 are preferably connected at a portion in the circumferential direction. More specifically, the refractory member 112 and the nozzle body 11 are preferably an integral refractory material, and the slits 40b are preferably formed by subjecting this integral refractory material to cutting or the like. This makes it possible to make the slits 40b less susceptible to deformation.

[0058] The long nozzle 40 according to the third embodiment of the present invention has been described above. This embodiment also makes it possible to effectively prevent air from entering the long nozzle 40.

[0059] [Other embodiments] The first to third embodiments have been described above, but these configurations are merely examples. The long nozzle has a slit width b of 0.5 mm or more and 2.0 mm or less, and the slit has a structure that suppresses deformation due to thermal expansion. Preferably, the long nozzle has a slit width b that changes by 1.0 mm or less before and after an operation in which molten steel at approximately 1600°C is passed through it. The change in slit width b before and after the operation is more preferably 0.5 mm or less.

[0060] In the above embodiments, the long nozzle is described as including the nozzle body 11 made of a refractory material and the case 12 made of a metal, but this configuration is merely an example. For example, the long nozzle may be entirely made of a refractory material. [Example]

[0061] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0062] [Lab Exam] Tests to verify the purging effect were conducted using several long nozzles with different slit widths (b). Figure 9 is a block diagram of the test equipment used in this test, and Figure 10 is a schematic diagram of this equipment. Only the upper 300 mm section of the long nozzle was used (the lower end was cut off), and the opening at the lower end was covered and blocked with an airtight container. The upper end of the molten steel injection port of the bottom nozzle was connected to a gas hose, and a pump, flow meter, pressure gauge, and oxygen concentration meter were also connected.

[0063] Ar gas was supplied at 100 NL / min through the gas inlet pipe of the long nozzle. A pump was used to aspirate gas (a mixture of Ar gas as a purge gas and air entering through the fitting) at 10 NL / min from the top of the molten steel inlet of the lower nozzle. This aspirating rate was the assumed flow rate entrained by the molten steel flow. The oxygen concentration of the aspirated gas was continuously analyzed, and the amount of air aspirated was calculated from the steady-state oxygen concentration to verify the purging effect.

[0064] Figure 11 shows the test results. As shown in Figure 11, there was an optimal value for the slit width b that minimized the amount of air suction. When the target air suction amount was set to 2.0 NL / min or less, it was found that the target could be met by setting the slit width b to between 0.5 mm and 2.0 mm. Furthermore, when the target air suction amount was set to 1.2 NL / min or less, it was found that the target could be met by setting the slit width b to between 0.8 mm and 1.6 mm. This optimal range for the slit width b did not change even when the Ar flow rate was changed from 100 NL / min to 300 NL / min.

[0065] [Actual machine test] Next, a test was conducted to pour molten steel into a tundish using a long nozzle with a structure similar to that described in Figure 4. The slit width b was 1.2 mm and the case thickness t was 4.5 mm. Ar gas was used as the purge gas. The original pressure of the Ar gas was approximately 0.1 MPa (gauge pressure) and the total flow rate was 300 NL / min. Using this long nozzle, molten steel was poured into the tundish from a 105-ton molten steel ladle at a rate of 3 t / min, and the amount of absorbed nitrogen was evaluated. The amount of absorbed nitrogen was evaluated as the difference in the analyzed value of the nitrogen content [N] between a metal sample collected after the secondary refining process (the upstream process) and a metal sample collected on the pouring side of the tundish. For comparison, similar tests were conducted using a long nozzle with a slit width b of 0.4 mm and a case thickness t of 3.2 mm (Comparative Example 1) and a long nozzle with a slit width b of 1.2 mm and a case thickness t of 3.2 mm (Comparative Example 2).

[0066] The results are shown in Table 1 and FIG.

[0067] [Table 1]

[0068] In the long nozzle of Comparative Example 1, which had a slit width b of 0.4 mm and a case thickness t of 3.2 mm, approximately 1 ppm of N absorption was observed. It is believed that air was entrained from the mating portion between the lower nozzle and the long nozzle, causing N absorption in the molten steel. Furthermore, in the long nozzle of Comparative Example 2, in which the case thickness t remained 3.6 mm and the slit width b was 1.2 mm, no improvement from Comparative Example 1 was observed. This was because the case was not rigid enough, causing the slit width b to change. On the other hand, in the long nozzle of the Example, the amount of N absorption was significantly reduced to approximately 0.4 ppm. It is believed that the amount of air entrainment was significantly reduced by increasing the slit width b to 1.2 mm and the case thickness to 4.5 mm, thereby increasing the stiffness.

[0069] Although the embodiments of the present invention have been described above, the above-described embodiments are merely examples for carrying out the present invention. Therefore, the present invention is not limited to the above-described embodiments, and the above-described embodiments can be appropriately modified and carried out within the scope of the invention. [Explanation of symbols]

[0070] 1. Continuous casting equipment 10, 30, 40 long nozzle 10a Pressure equalization room 10b, 30b, 40b slit 11 Nozzle body 111 Upper end 112 Refractory components 11a Recess 12 cases 12a opening 121, 321 (slit and adjacent) 322 Metallic components 323 Spacer 13 Gas inlet pipe 21 Molten Steel Ladle 22 Molten steel discharge device 221 Lower Nozzle 23 Tundish 24 Submerged Entry Nozzle 25 Mold

Claims

1. A long nozzle connected to a lower nozzle of a molten steel discharge device of a molten steel ladle, a slit for injecting gas from a radially outer side of the lower nozzle toward the lower nozzle; The width b of the slit is 0.5 mm or more and 2.0 mm or less, A long nozzle, wherein the slit has a structure that suppresses deformation due to thermal expansion.

2. The long nozzle according to claim 1, a nozzle body made of a refractory material; a metal case covering a portion of the upper end of the nozzle body, the slit is formed by an upper end of the nozzle body and the case, A long nozzle, wherein the thickness t of the portion of the case adjacent to the slit is 4.0 mm or more.

3. The long nozzle according to claim 1, a nozzle body made of a refractory material; a metal case covering a portion of the upper end of the nozzle body; a metal member disposed between an upper end of the nozzle body and the case; a spacer disposed between a portion of the case adjacent to the slit and the metal member, the slit is formed by the metal member and the case, A long nozzle, wherein the spacer is fixed to both a portion of the case adjacent to the slit and the metal member.

4. The long nozzle according to claim 3, A long nozzle, wherein the metal member is fixed to the case.

5. The long nozzle according to claim 1, a nozzle body made of a refractory material; a refractory member disposed above the nozzle body, A long nozzle, wherein the slit is formed by the refractory member and the upper end of the nozzle body.

6. The long nozzle according to claim 5, A long nozzle in which the refractory member and the nozzle body are an integral refractory material.

7. The long nozzle according to any one of claims 1 to 6, A long nozzle in which the width b of the slit is 0.8 mm or more and 1.6 mm or less.

8. A method for producing a slab, comprising the step of producing a slab using a continuous casting device including the long nozzle according to any one of claims 1 to 6.

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