Method and structure for connecting a reflux pipe and an immersion pipe

Abstract

To provide a method for connecting a circular flow tube to an immersion tube capable of preventing a situation in which molten metal enters through a gap between the inside of the circular flow tube and the inside of the immersion tube at an initial stage of molten steel treatment under reduced pressure and damages a refractory or iron skin of the circular flow tube and the immersion tube.SOLUTION: A cylindrical body 5a is provided at the lower end of a circular flow tube 1 of a vacuum degassing device, and a refractory brick coupling body 9 having a smaller inner diameter than the cylindrical body 5a is provided at the upper end edge of an immersion tube 2 to be mounted. When the immersion tube 2 is connected to the circular flow tube 1, the lower surface of the cylindrical body 5a of the circular flow tube 1 is brought into contact with the upper surface of the refractory brick coupling body 9 of the immersion tube 2, the refractory brick coupling body 9 of the immersion tube 2 is arranged concentrically with respect to the cylindrical body 5a of the circular flow tube 1, the circular flow tube 1 and the immersion tube 2 are bonded (bonding process), and thereafter, an amorphous refractory 10 is laminated on the inner peripheral surface of the cylindrical body 5a of the circular flow tube 1 so as to be flush with the inner peripheral surface of the refractory brick coupling body 9 (refractory laminating process).SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a method and structure for connecting a reflux pipe and a submerged pipe for treating molten steel used in a vacuum degassing apparatus. [Background technology]

[0002] A known vacuum degassing apparatus for degassing molten steel is an RH-type vacuum degassing apparatus, which consists of an upper vessel equipped with an inlet for feeding metals and the like and an exhaust port, a lower vessel, two reflux pipes attached to the bottom of the lower vessel, and immersion pipes connected to each reflux pipe. This vacuum degassing apparatus has two immersion pipes immersed in molten steel (molten metal) contained in a ladle, and Ar gas is supplied into one of the reflux pipes and immersion pipes, which function as upflow pipes. The molten steel is introduced into the vacuum region of the lower vessel along with the ascending current of the Ar gas, where it is degassed. The degassed molten steel is then discharged into the ladle through the other reflux pipe and immersion pipe, which function as downflow pipes. In addition, in order to make the connection process easier, a widely adopted method for connecting the reflux pipe and the immersion pipe in such a vacuum degassing apparatus is to abut and secure (screw) a flat donut-shaped flange provided at the upper end of the immersion pipe against a flat donut-shaped flange provided at the lower end of the reflux pipe.

[0003] The submerged pipe connected to the reflux pipe of such a vacuum degassing apparatus is severely damaged by the flow of molten steel during degassing and must therefore be periodically replaced. However, the flange at the bottom of the reflux pipe may bend due to thermal history during use. When the flange of the submerged pipe is joined to the flange of the reflux pipe in such a bent state, a gap G may form between the refractory material (firebricks) 55 inside the reflux pipe 51 and the refractory material (firebricks) 59 inside the submerged pipe 52, as shown in Figure 7. If a gap G is formed between the inside of the reflux pipe 51 and the inside of the submerged pipe 52, molten metal may enter through the gap G during the initial stage of molten steel treatment under reduced pressure, potentially damaging the refractory material 55 of the reflux pipe 51, the refractory material 59 of the submerged pipe 52, or the shell 53 covering the outer periphery of the reflux pipe 51 and the shell 56 covering the outer periphery of the submerged pipe 52.

[0004] In order to prevent molten metal from entering through the gap between the inside of the reflux pipe and the inside of the immersion pipe, a connection structure between the reflux pipe and the immersion pipe has been proposed, as disclosed in Patent Document 1, in which the lower end surface of the refractory material of the reflux pipe is positioned above the flange and the upper end surface of the refractory material of the immersion pipe is positioned above the flange. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-229800 Summary of the Invention [Problem to be solved by the invention]

[0006] The connection structure between the return flow pipe and the submerged pipe as disclosed in Patent Document 1 can prevent damage to the return flow pipe and the submerged pipe shell because it is unlikely that molten metal will seep through a gap between the return flow pipe refractory and the submerged pipe refractory and reach the shell, but it has the disadvantage that the lower end face of the return flow pipe refractory must be positioned above the flange, making it difficult to assemble the refractory near the lower end of the return flow pipe. Furthermore, in the connection structure between the return flow pipe and the submerged pipe as disclosed in Patent Document 1, an unexpected gap may form between the refractory protruding above the submerged pipe flange and the shell of the return flow pipe after connection, and molten metal may seep through the gap and damage the refractory of the return flow pipe or the submerged pipe or the shell of the return flow pipe or the submerged pipe.

[0007] The object of the present invention is to provide a method and structure for connecting a reflux pipe and an immersion pipe that solves the problems associated with the conventional methods and structures for connecting a reflux pipe and an immersion pipe described above, and that can accurately prevent molten metal from entering through the gap between the inside of the reflux pipe and the inside of the immersion pipe during the initial stage of molten steel processing under reduced pressure, thereby damaging the refractory or steel shell of the reflux pipe or immersion pipe. [Means for solving the problem]

[0008] The invention described in claim 1 is a method for connecting a reflux pipe and an immersion pipe provided near the lower end of a vacuum degassing apparatus, wherein the reflux pipe is provided with a cylindrical refractory near the lower end, and the immersion pipe is provided with a cylindrical refractory near the upper end, the cylindrical refractory having an inner diameter smaller than that of the cylindrical refractory near the lower end of the reflux pipe, and the method comprises the steps of: joining the reflux pipe and the immersion pipe in a state in which the lower surface of the cylindrical refractory near the lower end of the reflux pipe is brought into contact with the upper surface of the cylindrical refractory near the upper end of the immersion pipe, and the cylindrical refractory near the upper end of the immersion pipe is arranged concentrically with the cylindrical refractory near the lower end of the reflux pipe; and stacking a refractory material on the inner surface of the cylindrical refractory near the lower end of the reflux pipe so that it is flush with the inner surface of the cylindrical refractory near the upper end of the immersion pipe. The refractory layering step is performed by placing a cylindrical metal connecting auxiliary member having an outer diameter substantially the same as the inner diameter of the cylindrical refractory at the upper end of the immersion tube inside the cylindrical refractory at the upper end of the immersion tube, and by using the connecting auxiliary member, stacking the monolithic refractory on the inner peripheral surface of the cylindrical refractory at the lower end of the reflux tube, and the connecting auxiliary member has a truncated cone portion connected to the upper side of the cylindrical portion. It is characterized by the following.

[0010] Claim 2The invention described in claim 1 is characterized in that a magnesia-based or magnesia-spinel-based refractory is used as the monolithic refractory.

[0011] Claim 3 The invention described in the publication is a connection structure for connecting an immersion tube to a reflux tube provided near the lower end of a vacuum degassing apparatus, in which the reflux tube is provided with a cylindrical refractory material near the lower end, and the immersion tube is provided with a cylindrical refractory material near the upper end, the inner diameter of which is smaller than that of the cylindrical refractory material near the lower end of the reflux tube. The reflux tube and the immersion tube are joined in a state in which the lower surface of the cylindrical refractory material near the lower end of the reflux tube is in contact with the upper surface of the cylindrical refractory material near the upper end of the immersion tube, and the cylindrical refractory material near the upper end of the immersion tube is arranged concentrically with the cylindrical refractory material near the lower end of the reflux tube. A monolithic refractory material is provided on the inner surface of the cylindrical refractory material near the lower end of the reflux tube so as to be flush with the inner surface of the immersion tube. The reflux tube and the submerged tube are stacked together, and a connecting auxiliary member is disposed inside the connecting portion between the reflux tube and the submerged tube. The connecting auxiliary member is made of metal and has an outer diameter substantially the same as the inner diameter of the cylindrical refractory of the submerged tube, and has a shape in which a truncated cone-shaped portion is connected to the upper part of a cylindrical portion. It is characterized by the following. [Effects of the Invention]

[0012] According to the method of connecting a reflux pipe and an immersion pipe described in claim 1, even if the flange of the reflux pipe has become distorted due to use, the gap between the inside of the reflux pipe and the inside of the immersion pipe is blocked by the castable refractory, thereby effectively preventing damage to the refractory and steel shell caused by molten metal entering through the gap during the initial stage of molten steel processing under reduced pressure.

[0013] Also, claim 1 According to the method of connecting a reflux pipe and an immersion pipe described above, a connecting auxiliary member is placed inside a cylindrical refractory material near the upper end of the immersion pipe, and an amorphous refractory material is stacked on the inner surface of the cylindrical refractory material near the lower end of the reflux pipe, thereby making the construction of connecting the reflux pipe and the immersion pipe extremely easy.

[0014] Claim 2According to the method of connecting the reflux tube and the submerged tube described above, the gap between the inside of the reflux tube and the inside of the submerged tube is sealed with a highly heat-resistant magnesia-based refractory or a magnesia-spinel-based refractory, making it possible to more accurately prevent molten metal from entering through the gap during the initial stage of molten steel processing under reduced pressure.

[0015] Claim 3 According to the connection structure between the reflux pipe and the submerged pipe described above, even if the flange of the reflux pipe has become distorted during use, the gap between the inside of the reflux pipe and the inside of the submerged pipe is blocked by the monolithic refractory, making it possible to effectively prevent damage to the refractory and steel shell caused by molten metal entering through the gap during the initial stage of molten steel processing under reduced pressure. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 2 is an explanatory diagram (vertical cross-sectional view) showing a vacuum degassing device. [Figure 2] FIG. 2 is an explanatory diagram showing a circulation tube (a is a vertical cross-sectional view, and b is a cross-sectional view taken along line AA in a). [Figure 3] 1A and 1B are explanatory views showing an immersion tube (a is a vertical cross-sectional view, and b is a cross-sectional view taken along line BB in a). [Figure 4] FIG. 10 is an explanatory diagram (vertical cross section) showing how an immersion tube is connected to a reflux tube. [Figure 5] 1A and 1B are explanatory views showing a connection auxiliary member (FIG. 1A is a vertical cross-sectional view, and FIG. 1B is a plan view). [Figure 6] 1A and 1B are explanatory diagrams showing the connection structure between the reflux pipe and the immersion pipe (a is a vertical cross-sectional view, b is an enlarged view of part C in a, and c is a cross-sectional view along line DD in a). [Figure 7] FIG. 1 is an explanatory diagram (vertical cross section) showing a conventional connection structure between a reflux pipe and an immersion pipe. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, an embodiment of a method and structure for connecting a reflux tube and an immersion tube according to the present invention will be described in detail with reference to the drawings.

[0018] <Structure of reflux tube> FIG. 1 shows a vacuum degassing apparatus for removing gas components from molten steel. Two reflux pipes 1, 1 are installed vertically side by side at the bottom of the lower vessel of the vacuum degassing apparatus M. FIG. 2 shows the reflux pipe 1. The reflux pipe 1 is composed of a cylindrical refractory brick stack 5 formed by assembling many refractory bricks, a steel shell 3 covering the outer periphery of the refractory brick stack 5, and castable refractory filling the gap between the refractory brick stack 5 and the steel shell 3. As shown in FIG. 2(b), the refractory brick stack 5 is formed by concentrically stacking flat cylindrical bodies 5a, 5b, 5c, etc., each of which is made up of many refractory bricks 11, 11, etc. assembled in a doughnut shape (bonded together with castable refractory). The steel shell 3 has a flattened cylindrical portion at its lower end, and a doughnut-shaped flange 4 is integrally formed at its lower edge.

[0019] <Structure of reflux tube> FIG. 3 shows the submerged pipe 2 connected to the reflux pipe 1. The submerged pipe 2 is composed of a refractory brick assembly 9 formed by integrally assembling numerous refractory bricks 11, 11..., a cylindrical shell 6 covering the outer periphery of the refractory brick assembly 9, and a castable refractory material 8 formed to fill the gap between the refractory brick assembly 9 and the shell 6 and to cover the outer periphery of the shell 6 and the underside of the refractory brick assembly 9. As shown in FIG. 3(b), the refractory brick assembly 9 is formed into a thick cylindrical shape by assembling (bonding with castable refractory material) numerous vertically elongated, approximately rectangular parallelepiped refractory bricks 11, 11.... Meanwhile, a doughnut-shaped flange 7 is integrally formed on the upper edge of the shell 6.

[0020] <Method of connecting the reflux tube and the immersion tube> Figure 4 shows how a new submerged tube 2 is connected (attached) to the reflux tube 1 installed near the lower end of the vacuum degassing apparatus M as described above. When connecting the reflux tube 1 and the submerged tube 2, first, as shown in Figure 4(a), the inner wall of the lowest cylindrical body 5a of the refractory brick stack 5 made of refractory bricks stacked inside the steel shell 3 of the reflux tube 1 is ground (polished) by a certain thickness. Then, the inner diameter of the lowest cylindrical body 5a is made larger by a certain length (approximately 20 to 200 mm) than the inner diameter of the upper cylindrical body 5b. Here, the method used is to first form the refractory brick stack 5, and then grind the inner wall of the lowest cylindrical body 5a in the refractory brick stack 5 by a certain thickness. However, it is also possible to previously form a cylindrical body 5a with an inner diameter larger than the inner diameters of the upper cylindrical bodies 5b and 5c (i.e., a cylindrical body 5a thinner than the cylindrical bodies 5b and 5c), and then set the cylindrical body 5 with the larger inner diameter in position a.

[0021] After grinding the inner wall of the lowest cylindrical body 5a inside the reflux pipe 1 as described above, the submerged pipe 2 is concentrically joined to the lower side of the reflux pipe 1 (joining process). That is, the lower surface of the flange 4 of the reflux pipe 1 is abutted against the flange 7 of the submerged pipe 2, and the flanges 4, 7 are fixed to each other (for example, by screwing them together with bolts and nuts). By joining the submerged pipe 2 to the lower side of the reflux pipe 1 in this manner, a cylindrical cavity C is formed inside the reflux pipe 1 and the submerged pipe 2.

[0022] Next, the auxiliary connection member 21 is inserted into the hollow portion C. FIG. 5 shows the auxiliary connection member 21, which is integrally formed into a cylindrical shape from metal (iron, etc.). The lower portion (cylindrical portion 22) of the auxiliary connection member 21 has an outer diameter that is approximately the same as the inner diameter of the immersion tube 2, and the upper portion is formed into a truncated cone shape so that the diameter gradually decreases from bottom to top. The outer surface of the truncated cone portion 23 is inclined at approximately 30° with respect to the vertical plane. When inserting the auxiliary connection member 21 into the hollow portion C, the auxiliary connection member 21 is positioned so that the boundary line B between the cylindrical portion 22 and the truncated cone portion 23 of the auxiliary connection member 21 is located inside the lowest cylindrical body 5a of the circulation tube 1, as shown in FIG. 4(b). Then, the auxiliary connection member 21 is fixed (adhered) to the immersion tube 2.

[0023] After inserting the auxiliary connection member 21 into the hollow portion C of the reflux pipe 1 and the submerged pipe 2 as described above, as shown in FIG. 4(c), a monolithic refractory (magnesia-based or magnesia-spinel-based refractory (castable)) 10 is poured into the gap between the inner wall of the lowest cylindrical body 5a of the reflux pipe 1 and the truncated cone-shaped portion 23 of the auxiliary connection member 21 (monolithic refractory layering process). The monolithic refractory 10 is then allowed to fully harden, thereby completing the connection process. When pouring the monolithic refractory 10 into the gap between the inner wall of the lowest cylindrical body 5a of the reflux pipe 1 and the truncated cone-shaped portion 23 of the auxiliary connection member 21 as described above, a synthetic resin tube or the like can be suitably used.

[0024] Figure 6 shows the state in which the reflux pipe 1 and the dip pipe 2 are connected. The flange 4 of the reflux pipe 1 has become distorted during use, creating a gap between the flange 4 and the flange 7 of the dip pipe 2. This has resulted in a gap G between the underside of the lowest cylindrical body 5a of the reflux pipe 1 and the upper surface of the refractory brick assembly 9 of the dip pipe 2. However, this gap G is now blocked by the castable refractory 10 poured into the gap between the inner wall of the lowest cylindrical body 5a of the reflux pipe 1 and the truncated cone portion 23 of the connecting support member 21. As shown in Figure 6(b), the castable refractory 10 has penetrated into the gap G between the underside of the lowest cylindrical body 5a of the reflux pipe 1 and the upper surface of the refractory brick assembly 9 of the dip pipe 2.

[0025] <Effects of the vacuum degassing device> In the vacuum degassing apparatus M, in which the submerged pipes 2, 2 are connected below the return pipes 1, 1 as described above, the lower ends of the submerged pipes 2, 2 are immersed in the molten metal (molten steel) in a ladle (not shown). One of the return pipes 1 functions as an uprising pipe together with the submerged pipe 2, and the other return pipe 1 functions as a downcomer together with the submerged pipe 2. When a vacuum is created inside the apparatus and an inert gas such as argon gas is blown into the uprising pipes (one of the return pipes 1 and submerged pipe 2) via piping (not shown), the molten metal in the ladle is drawn into the lower vessel and rises inside the uprising pipe, then descends inside the downcomer pipes (the other return pipes 1 and submerged pipe 2) and returns to the ladle to be circulated. During this circulating process, the molten metal is degassed, and the degassed gas is discharged to the outside.

[0026] In the connection structure between the reflux pipe 1 and the immersion pipe 2 described above, the gap G between the inside of the reflux pipe 1 and the inside of the immersion pipe 2 (the gap between the lower surface of the refractory brick stack 5 of the reflux pipe 1 and the upper surface of the refractory brick combination 9 of the immersion pipe) is blocked by the monolithic refractory 10, so that when the vacuum degassing apparatus M is used as described above, molten metal does not enter the gap G. Furthermore, the connection auxiliary member 21 in the connection structure between the reflux pipe 1 and the immersion pipe 2 described above dissolves in the molten metal and disappears in a very short time during use of the vacuum degassing apparatus M, so that the connection auxiliary member 21 does not obstruct the flow of molten metal flowing inside the uprising pipe and downcomer pipe.

[0027] <Connection method between reflux tube and immersion tube / Effect of connection structure> The above-mentioned method of connecting the reflux pipe 1 and the immersion pipe 2 is such that the reflux pipe 1 has a cylindrical refractory material (firebrick stack 5) at its lower end, and the immersion pipe 2 has a cylindrical refractory material (firebrick combination 9) at its upper end that has an inner diameter smaller than that of the cylindrical refractory material (cylindrical body 5a) at its lower end. The above-mentioned method of connecting the reflux tube 1 and the immersion tube 2 includes a joining process in which the lower surface of the cylindrical body 5a at the lower end of the reflux tube 1 is abutted against the upper surface of the refractory brick combination 9 at the upper end of the immersion tube 2, and the refractory brick combination 9 at the upper end of the immersion tube 2 is arranged concentrically with the cylindrical body 5a at the lower end of the reflux tube 1, and a refractory stacking process in which amorphous refractory 10 is stacked on the inner surface of the cylindrical body 5a at the lower end of the reflux tube 1 so that it is flush with the inner surface of the refractory brick combination 9 at the upper end of the immersion tube 2.

[0028] Therefore, according to this connection method, even if the flange 4 of the reflux pipe 1 has become distorted due to use, the gap G between the inside of the reflux pipe 1 and the inside of the immersion pipe 2 is blocked by the amorphous refractory 10, thereby effectively preventing damage to the refractory materials (such as the refractory brick stack 5 and refractory brick combination 9), the steel shell 3 of the reflux pipe 1, and the steel shell 6 of the immersion pipe 2 caused by molten metal entering through the gap G during the initial stage of molten steel processing under reduced pressure.

[0029] In addition, the above-mentioned method of connecting the reflux pipe 1 and the immersion pipe 2 involves placing a cylindrical metal connecting auxiliary member 21 having an outer diameter approximately the same as the inner diameter of the refractory brick combination 9 inside the refractory brick combination 9 at the upper end of the immersion pipe 2, and using this connecting auxiliary member 21 to stack amorphous refractory material 10 on the inner surface (inner wall surface) of the cylindrical body 5a at the lower end of the reflux pipe 1, making the construction of connecting the reflux pipe 1 and the immersion pipe 2 very easy.

[0030] Furthermore, since the above-mentioned method of connecting the reflux pipe 1 and the immersion pipe 2 uses a magnesia-based or magnesia-spinel-based refractory (castable) as the monolithic refractory 10, the gap G between the inside of the reflux pipe 1 and the inside of the immersion pipe 2 (the gap G between the lower surface of the refractory brick stack 5 of the reflux pipe 1 and the upper surface of the refractory brick combination 9 of the immersion pipe 2) is blocked by a highly heat-resistant magnesia-based refractory or magnesia-spinel-based refractory, thereby making it possible to more accurately prevent molten metal from entering through the gap G between the inside of the reflux pipe 1 and the inside of the immersion pipe 2 during the initial stage of molten steel processing under reduced pressure.

[0031] In addition, the above-mentioned method of connecting the reflux pipe 1 and the immersion pipe 2 uses a connecting auxiliary member 21 having a shape in which a truncated cone-shaped portion 23 is connected to the upper side of a cylindrical portion 22, so that the monolithic refractory material 10 can be very easily poured into the gap S between the inner wall of the cylindrical body 5a at the lowest position of the reflux pipe 1 and the truncated cone-shaped portion 23 of the connecting auxiliary member 21.

[0032] On the other hand, the connection structure between the above-mentioned reflux tube 1 and the immersion tube 2 is such that the reflux tube 1 has a cylindrical body 5a at its lower end, and the immersion tube 2 has a refractory brick combination 9 at its upper end, which has an inner diameter smaller than that of the cylindrical body 5a at the lower end of the reflux tube 1.The reflux tube 1 and the immersion tube 2 are joined in a state in which the lower surface of the cylindrical body 5a at the lower end of the reflux tube 1 abuts against the upper surface of the refractory brick combination 9 at the upper end of the immersion tube 2, and the refractory brick combination 9 at the upper end of the immersion tube 2 is arranged concentrically with the cylindrical body 5a at the lower end of the reflux tube 1.A castable refractory material 10 is stacked on the inner surface of the cylindrical body 5a at the lower end of the reflux tube 1 so that it is flush with the inner surface of the immersion tube 2.

[0033] Therefore, with this connection structure, even though the flange 4 of the reflux pipe 1 becomes distorted during use and a gap G is formed between the inside of the reflux pipe 1 and the inside of the immersion pipe 2, this gap G is blocked by the monolithic refractory material 10, so damage to the refractory materials (firebrick stack 5 and firebrick combination 9) and the steel shell 3 of the reflux pipe 1 and the steel shell 6 of the immersion pipe 2 caused by molten metal entering through the gap G during the initial stage of molten steel processing under reduced pressure can be effectively prevented.

[0034] <Example of changing the dip tube> The immersion pipe of the present invention is not limited to the above-described embodiment, and the material, shape, structure, size, and other configurations of the reflux pipe (iron shell, refractory brick stack, flange) and the immersion pipe (iron shell, refractory brick combination, monolithic refractory material) can be appropriately modified as necessary within the scope of the present invention.

[0035] For example, the immersion pipe used in the connection method and connection structure according to the present invention is not limited to the above embodiment having a refractory brick assembly formed into a thick cylindrical shape by assembling a large number of refractory bricks in a substantially rectangular parallelepiped shape, but may be one having a refractory brick assembly integrally formed into a thick cylindrical shape, etc. Furthermore, the immersion pipe is not limited to the above embodiment having a single layer of refractory brick assembly, but may be one having multiple layers of refractory brick assembly.

[0036] Furthermore, the connection method and connection structure between the reflux tube and the immersion tube according to the present invention is not limited to the use of a magnesia-based or magnesia-spinel-based refractory (castable) as the amorphous refractory to be filled in the gap between the inner wall of the cylindrical body at the lowest position of the reflux tube and the upper truncated cone-shaped portion of the connecting auxiliary member, as in the above embodiment, but it is also possible to use alumina-based or magnesia-chromium-based refractories (castable, etc.) as the amorphous refractory.

[0037] Furthermore, the method and structure for connecting the reflux tube and the submerged tube according to the present invention is not limited to the above embodiment, in which a connecting auxiliary member is used, which is a truncated cone-shaped portion connected to the upper side of a cylindrical portion, but may also be a simple cylindrical connecting auxiliary member, etc. In addition, the method for connecting the reflux tube and the submerged tube according to the present invention is not limited to the above embodiment, in which a connecting auxiliary member is inserted into the submerged tube joined to the reflux tube, but may also be a method in which an submerged tube with a connecting auxiliary member inserted into it in advance is joined to the reflux tube, etc. [Industrial Applicability]

[0038] The connection method and structure between a reflux pipe and an immersion pipe according to the present invention has the excellent effects described above, and can therefore be suitably used as a connection method and structure between a reflux pipe and an immersion pipe when replacing an immersion pipe in a vacuum degassing apparatus after it has been used for a certain period of time with a new one. [Explanation of symbols]

[0039] 1...reflux tube 2...dip tube 4. Flange 5. Refractory brick laminate 5a,5b,5c...Cylindrical body 7. Flange 8. Monolithic refractories 9. Refractory brick composite 11. Firebrick 21. Connection auxiliary member 22 Cylindrical part 23. Cone-shaped part M··Vacuum degassing equipment

Claims

1. A method for connecting a reflux pipe and a dip pipe provided at the lower end of a vacuum degassing apparatus, comprising: The reflux tube has a cylindrical refractory material at the bottom end, The immersion tube has a cylindrical refractory member at its upper end, the cylindrical refractory member having an inner diameter smaller than that of the cylindrical refractory member at the lower end of the reflux tube, a joining step of joining the reflux tube and the submerged tube in a state in which the lower surface of the cylindrical refractory material at the lower end of the reflux tube and the upper surface of the cylindrical refractory material at the upper end of the submerged tube are brought into contact with each other, and the cylindrical refractory material at the upper end of the submerged tube is arranged concentrically with the cylindrical refractory material at the lower end of the reflux tube; and a refractory layering step of layering a monolithic refractory on an inner peripheral surface of a cylindrical refractory at the lower end of the reflux tube so as to be flush with an inner peripheral surface of a cylindrical refractory at the upper end of the immersion tube, The refractory layering step is a step of placing a cylindrical metal connecting auxiliary member having an outer diameter substantially the same as the inner diameter of the cylindrical refractory at the upper end of the immersion tube inside the cylindrical refractory at the upper end of the immersion tube, and using the connecting auxiliary member, stacking the monolithic refractory on the inner peripheral surface of the cylindrical refractory at the lower end of the reflux tube, and A method for connecting a reflux pipe and an immersion pipe, characterized in that the connection auxiliary member comprises a cylindrical portion and a truncated cone portion connected to the upper side of the cylindrical portion.

2. 2. The method for connecting a reflux tube and an immersion tube according to claim 1, wherein the monolithic refractory is a magnesia-based or magnesia-spinel-based refractory.

3. A connection structure for connecting a dip tube to a reflux pipe provided at the lower end of a vacuum degassing apparatus, The reflux tube has a cylindrical refractory material at the bottom end, The immersion tube has a cylindrical refractory member at its upper end, the cylindrical refractory member having an inner diameter smaller than that of the cylindrical refractory member at the lower end of the reflux tube, The reflux tube and the immersion tube are joined in a state in which the lower surface of the cylindrical refractory material at the lower end of the reflux tube is in contact with the upper surface of the cylindrical refractory material at the upper end of the immersion tube, and the cylindrical refractory material at the upper end of the immersion tube is concentrically arranged with the cylindrical refractory material at the lower end of the reflux tube, A monolithic refractory material is laminated on the inner surface of the cylindrical refractory material at the lower end of the reflux tube so as to be flush with the inner surface of the immersion tube, and A connection structure between a reflux pipe and an immersion pipe, characterized in that a connection auxiliary member made of metal and having an outer diameter approximately the same as the inner diameter of the cylindrical refractory material of the immersion pipe, and having a shape consisting of a truncated cone portion connected to the upper part of a cylindrical portion, is disposed inside the connection portion between the reflux pipe and the immersion pipe.

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