Circulation pipe mounting structure in the lower vessel of a vacuum degassing device

Abstract

To provide a reflux tube fitting structure to a lower tank of a vacuum degassing apparatus, even when a steel sheet covering each reflux tube is tilted by thermal deformation, capable of easily fitting the same to a lower face of an isolation part of a lower tank without executing many cuttings to the isolation part and each reflux tube and easily executing the replacement operation of each eroded reflux tube.SOLUTION: In a lower tank 1 of a vacuum degassing apparatus, an insole part 3 is formed into a thick planar shape obtained by drilling a through hole with reflux tubes 5, 5, also the circumference of the through hole with the reflux tubes 5, 5 in a lower face of the isolation part 3 is formed into a recessed spherical shape, and the surface of each reflux tube 5, 5 is formed into a projecting spherical shape with a curvature radius same as that of the recessed spherical face at the lower face of the insole part 3.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a mounting structure for mounting a reflux tube to a bottom portion of a lower vessel of a vacuum degassing apparatus for treating molten steel. [Background technology]

[0002] A known vacuum degassing apparatus for degassing molten steel is an RH-type vacuum degassing apparatus, which includes an upper vessel equipped with an inlet for charging alloys, auxiliary materials, etc., and an exhaust port, a lower vessel formed by a cylindrical body with a bottom and two reflux tubes attached to the bottom, and an immersion tube connected to the lower end of each reflux tube for immersion in the molten steel. As described in Patent Document 1, the lower vessel of the vacuum degassing apparatus has a cylindrical shell with a bottom, and side walls and a bottom wall of a predetermined thickness formed by assembling refractory bricks inside the shell. Two cylindrical reflux tubes, also made of refractory bricks, are installed in the bottom wall so as to penetrate the bottom wall. The outer peripheries of the reflux tubes are covered by the shell. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-254120 Summary of the Invention [Problem to be solved by the invention]

[0004] In vacuum degassing apparatuses such as those described above, the reflux tube melts after a certain period of use, requiring periodic replacement of either the entire lower vessel (the inner sidewall and bottom portion of the shell) or just the reflux tube. However, in the lower vessel of a conventional vacuum degassing apparatus such as that described in Patent Document 1, if the shell covering the reflux tube is tilted due to thermal deformation, the reflux tube, which has been inserted through the tilted shell, cannot be inserted into the insertion hole in the bottom portion, as shown in FIG. 7. Therefore, part of the bottom portion must be cut (to insert the reflux tube deep into the insertion hole in the bottom portion), and the upper part of the reflux tube must be cut and then filled with castable refractory material. This makes the replacement of the reflux tube extremely time-consuming.

[0005] The object of the present invention is to provide a reflux pipe mounting structure for a lower vessel that solves the problems associated with the lower vessel of the above-mentioned conventional vacuum degassing apparatus, and that can be easily attached to the underside of the base of the lower vessel without cutting the base or the reflux pipe, even when the steel shell covering the reflux pipe has become tilted due to thermal deformation, thereby facilitating the replacement of the reflux pipe. [Means for solving the problem]

[0006] The present invention, as set forth in claim 1, provides a mounting structure for mounting the reflux tubes to the bottom portion of a lower vessel in a vacuum degassing apparatus, in which two cylindrical reflux tubes are attached to the bottom portion of a lower vessel of a vacuum vessel and the reflux tubes and the lower vessel are covered with an iron shell, characterized in that the bottom portion is formed as a thick plate having communication holes with the reflux tubes, the periphery of the communication holes on the underside of the bottom portion is formed as a concave sphere, and the outer circumferential surface of the upper end of the reflux tube is formed as a convex sphere having the same radius of curvature as the concave sphere on the underside of the bottom portion.

[0007] The invention described in claim 2 is characterized in that in the invention described in claim 1, the bottom part of the lower tank is formed by laying precast blocks.

[0008] The invention described in claim 3 is the invention described in claim 1 or 2, characterized in that the reflux pipe is an integral part of a precast block. [Effects of the Invention]

[0009] According to the attachment structure for the reflux pipe in the lower vessel of an RH degassing apparatus (hereinafter simply referred to as the attachment structure for the reflux pipe), when replacing a damaged reflux pipe with a new one, even if the shell covering the reflux pipe is tilted due to thermal deformation, the reflux pipe can be inserted deep into the tilted shell, and the convex spherical surface on the outer periphery near the upper end can be joined to the concave spherical surface around the communicating hole in the bottom part. Therefore, according to the attachment structure for the reflux pipe described in claim 1, the bottom part and the reflux pipe can be easily attached to the underside of the bottom part 3 without extensive cutting, using a lot of monolithic refractory (for filling), or restoring the deformation of the shell.

[0010] In the reflux pipe mounting structure described in claim 2, the bottom part of the lower tank is formed by laying precast blocks, so the periphery of the communication hole in the bottom part of the lower tank can be easily molded into a concave spherical shape, significantly reducing the amount of work required on site when replacing the reflux pipe. Also, because there is no need to use a lot of mortar (compared to laying a large amount of small firebricks), the reflux pipe can be dried in a short time after replacement, reducing the power consumption required for drying.

[0011] In the attachment structure for the return flow pipe described in claim 3, the return flow pipe is a single piece made of a precast block, so that the upper surface of the return flow pipe can be easily molded into a convex spherical shape, further reducing the amount of work required on site when replacing the return flow pipe. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 2 is an explanatory diagram (vertical cross-sectional view) showing the lower tank (the lower tank of the RH degassing device). [Figure 2]FIG. 10 is an explanatory diagram (perspective view) showing a state in which a reflux pipe is attached to the bottom plate of the lower tank. [Figure 3] FIG. 10 is an explanatory diagram (vertical cross-sectional view) showing a state in which a reflux pipe is attached to the bottom plate of a lower tank. [Figure 4] FIG. 10 is an explanatory diagram (vertical cross section) showing how a reflux tube is attached to the bottom plate of a lower vessel having an inclined steel shell. [Figure 5] FIG. 10 is an explanatory diagram (vertical cross section) showing a modified example of the attachment structure of the circulation pipe. [Figure 6] FIG. 10 is an explanatory diagram (vertical cross section) showing a modified example of the attachment structure of the circulation pipe. [Figure 7] FIG. 10 is an explanatory diagram showing a conventional attachment structure of a circulation pipe. DETAILED DESCRIPTION OF THE INVENTION

[0013] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a reflux pipe mounting structure in a vacuum degassing apparatus according to the present invention will be described in detail below with reference to the drawings.

[0014] <Circulation pipe mounting structure> FIG. 1 shows the lower vessel of a vacuum degassing apparatus for degassing molten steel. The lower vessel 1 is composed of a side wall 2 formed in the shape of a hollow cylinder, a thick disk-shaped bottom wall 3, two reflux tubes 5, 5 attached to the underside of the bottom wall 3, and a steel shell 4 covering the outer periphery of the side wall 2, bottom wall 3, and reflux tubes 5, 5.

[0015] The shell 4 is formed in a cylindrical shape with a bottom, and two cylindrical insertion portions 4c, 4c for inserting the return pipes 5, 5 are provided on the bottom plate 4d so as to protrude downward. A flange 4a for connecting to an upper tank (not shown) is provided on the upper end of the shell 4 so as to protrude outward, and a flange 4b ​​for connecting to a submerged pipe (not shown) is formed on the lower end of each insertion portion 4c, 4c.

[0016] The side wall 2 is formed into a hollow cylindrical shape of a predetermined thickness by assembling a plurality of precast blocks made of an alumina-based refractory material (for example, made of 70 to 95 mass % alumina and 5 to 30 mass % magnesia) formed into a predetermined shape (such as a shape obtained by dividing a flat cylinder in the radial direction relative to the central axis) inside the cylindrical shell 4. The space between the assembled side wall 2 and shell 4 is filled with a monolithic refractory material (castable material) (not shown).

[0017] 2 shows the base portion 3, which is formed into a disk shape of a predetermined thickness by assembling multiple precast blocks made of the same alumina-based refractory material as the side wall 2. Two circular insertion holes (communication holes) 3a, 3a for inserting the reflux pipes 5, 5 are drilled in the base portion 3 with their centers aligned in the diameter direction of the base portion 3. The reflux pipes 5, 5 are attached to the drilled portions of the insertion holes 3a, 3a.

[0018] 3 shows the mounting structure of the return flow pipes 5, 5 in the base portion 3. The periphery (inner peripheral surface) of each insertion hole 3a, 3a drilled in the base portion 3 is formed into a spherical shape (concave spherical shape) with a curvature radius r (i.e., 1 / 2 the outer diameter of the return flow pipe 5) centered on a predetermined point P on the central axis C of the return flow pipe 5, 5 to be inserted (spherical surface 3S). Point P is also the intersection point between the upper surface of the bottom plate 4d of the shell 4 and the central axis C of the return flow pipe 5.

[0019] On the other hand, each reflux pipe 5, 5 is a precast block integrally formed from the same alumina-based refractory material as the side wall 2 and the base portion 3, and is formed into a flat cylindrical shape with a predetermined thickness. The outer surface (outer peripheral surface) of each reflux pipe 5, 5 near the upper end is formed into a spherical shape (convex spherical shape) with a curvature radius r (i.e., 1 / 2 the outer diameter of the reflux pipe 5) centered on a predetermined point P on the central axis C (spherical surface 5S). The outer surface of each reflux pipe 5, 5 near the upper end is fitted around (inner peripheral surface) of each insertion hole 3a, 3a of the base portion 3, and is fixed in place with monolithic refractory (castable material).

[0020] <Function of the Circulation Pipe Mounting Structure> The lower vessel 1 of the vacuum degassing apparatus constructed as described above is fixed to an upper vessel (not shown) by means of a flange 4a at the upper end of the shell 4, and is connected to an immersion pipe (not shown) by means of a flange 4b ​​provided at the lower end of each insertion portion 4c of the shell 4, and is used as a vacuum degassing apparatus for degassing molten steel. After the vacuum degassing apparatus has been used for a certain period of time, if the reflux tubes 5, 5 are damaged by the heat of the molten steel, it will be necessary to replace them with new reflux tubes 5, 5 of the same shape.

[0021] When replacing such damaged reflux tubes 5, 5 with new ones, the shell 4 is often deformed by heat after a certain period of use and tilted relative to the bottom plate 4d. Even in such cases, because the outer peripheral surface of each reflux tube 5, 5 near its upper end is formed in a convex spherical shape, it is possible to insert the tube deeply into the insertion portion 4c of the tilted shell 4, as shown in Figure 4, so that the outer peripheral surface 5S near its upper end abuts (close enough to allow bonding) against the concave spherical peripheral surface 3S around the insertion hole 3a of the bottom portion 3. Therefore, when installing new reflux tubes 5, 5, it is not necessary to cut the outer peripheries of the bottom portion 3 or the reflux tubes 5, 5, use a large amount of monolithic refractory (for filling), or restore the deformation of the shell 4.

[0022] <Effects of the circulation tube mounting structure> As described above, the mounting structure of the return flow pipes 5, 5 in the lower tank 1 is such that the base portion 3 is formed as a thick plate with insertion holes 3a, 3a that communicate with the return flow pipes 5, 5, the periphery of the insertion holes 3a, 3a on the underside of the base portion 3 is formed as a concave spherical surface, and the outer circumferential surface of each return flow pipe 5, 5 near its upper end is formed as a convex spherical surface with the same radius of curvature as the concave spherical surface on the underside of the base portion 3. Therefore, with this mounting structure of the return flow pipes 5, 5, even if the shell 4 covering the return flow pipe 5, 5 has tilted due to thermal deformation when replacing a damaged return flow pipe 5, 5, the return flow pipe 5, 5 can be inserted deep into the tilted shell 4, and the convex spherical surface 5S on the outer circumferential surface near its upper end can be joined to the concave spherical surface 3S around the insertion holes 3a, 3a of the base portion 3. Therefore, according to the mounting structure of the reflux pipes 5, 5, the bottom part 3 and the reflux pipes 5, 5 can be easily mounted to the underside of the bottom part 3 without having to cut a lot, use a lot of castable refractory material (for filling), or restore deformation of the steel shell 4.

[0023] Furthermore, the mounting structure of the reflux pipes 5, 5 in the lower tank 1 is formed by laying the base 3 using precast blocks, so the periphery of the communication holes 3a, 3a of the base 3 can be easily molded into a concave spherical shape, significantly reducing the amount of work required on-site when replacing the reflux pipes 5, 5. Furthermore, because there is no need to use a large amount of mortar, the reflux pipes 5, 5 can be dried in a short time after replacement, which also reduces the power consumption required for drying.

[0024] Furthermore, the mounting structure of the return pipes 5,5 in the lower tank 1 is such that the return pipes 5,5 are made of a single precast block, so that the outer surfaces of the upper ends of the return pipes 5,5 can be easily molded into a convex spherical shape, further reducing the amount of work required on site when replacing the return pipes.

[0025] <Example of modified installation structure of circulation pipe> The attachment structure of the reflux pipe according to the present invention is not limited to the above-described embodiment, and the materials, shapes, sizes, and other configurations of the lower tank, reflux pipe, iron shell, etc. can be appropriately changed as needed within the scope of the present invention.

[0026] For example, the mounting structure for the return flow tube according to the present invention is not limited to the above embodiment, in which the periphery of the through hole (insertion hole) in the base portion is a concave spherical surface with a radius of curvature that is half the outer diameter of the return flow tube and is centered at the intersection of the upper surface of the bottom plate of the iron shell and the central axis of the return flow tube, and the outer peripheral surface at the upper end of the return flow tube is a convex spherical surface with the same radius of curvature (i.e., a radius of curvature that is half the outer diameter of the return flow tube) as the concave spherical surface and centered at the same point as the concave spherical surface (i.e., the intersection of the upper surface of the bottom plate of the iron shell and the central axis of the return flow tube). The shapes of the concave spherical surface around the through hole in the base portion and the convex spherical surface around the outer peripheral surface at the upper end of the return flow tube can be changed as needed.

[0027] For example, as shown in Figure 5, the periphery of the communication hole in the bottom portion may be a concave spherical surface with a radius of curvature r equal to half the outer diameter of the return flow tube and centered at position P' below the intersection of the top surface of the bottom plate of the shell and the central axis of the return flow tube, and the outer surface of the return flow tube near the top end may be a convex spherical surface with a radius of curvature r equal to the concave spherical surface and centered at the same position P' as the concave spherical surface, thereby forming a vertical cylindrical portion near the top end of the communication hole in the bottom portion and causing a part of the bottom portion to protrude into the insertion portion of the shell. Alternatively, as shown in Figure 6, the periphery of the communication hole in the bottom portion may be a concave spherical surface with a radius of curvature r' equal to half the outer diameter of the return flow tube and centered at position P" below the intersection of the top surface of the bottom plate of the shell and the central axis of the return flow tube, and the outer surface of the return flow tube near the top end may be a convex spherical surface with a radius of curvature r' equal to the concave spherical surface and centered at the same position P" as the concave spherical surface.

[0028] In addition, the mounting structure for the reflux pipe according to the present invention does not require the concave spherical surface around the communicating hole in the base portion and the convex spherical surface on the outer peripheral surface at the upper end of the reflux pipe to have exactly the same radius of curvature, as in the above embodiment. Taking into account factors such as the thickness of the adhesive used when adhering the convex spherical surface on the outer peripheral surface at the upper end of the reflux pipe to the concave spherical surface around the communicating hole in the base portion, it is also possible to make the radius of curvature of the concave spherical surface around the communicating hole in the base portion slightly larger (by 5% or less) than the convex spherical surface on the outer peripheral surface at the upper end of the reflux pipe.

[0029] Furthermore, as in the above embodiment, the mounting structure of the reflux pipe according to the present invention is formed by assembling precast blocks of the same alumina-based refractory material as the side walls and bottom portion, and is not limited to reflux pipes that are precast blocks of the same alumina-based refractory material as the side walls and bottom portion. The materials used to form the side walls, bottom portion, and reflux pipe can be changed as needed, and it is also possible to replace part or all of the side walls, bottom portion, and part of the reflux pipe with firebricks or monolithic refractories. [Industrial Applicability]

[0030] The reflux pipe mounting structure according to the present invention has the excellent effects as described above, and can be suitably used when manufacturing or repairing the lower vessel of a vacuum degassing apparatus. [Explanation of symbols]

[0031] 1. Lower chamber of vacuum degassing device 2...side wall 3. Bottom 3a: Through hole (communicating hole) 3S: Concave spherical surface 4...Ironhide 5.Recirculation tube 5S: Convex spherical surface

Claims

1. In a vacuum degassing apparatus in which two cylindrical reflux tubes are attached to a bottom portion of a lower vessel of a vacuum vessel, and the reflux tubes and the lower vessel are covered with an iron shell, an attachment structure for attaching the reflux tubes to the bottom portion of the lower vessel, comprising: The base portion is formed in a thick plate shape with a communication hole with the reflux pipe drilled therein, and the periphery of the communication hole on the underside of the base portion is formed in a concave spherical shape, 1. A mounting structure for a reflux tube in a lower vessel of a vacuum degassing apparatus, characterized in that the outer peripheral surface of the reflux tube near the upper end is formed into a convex spherical shape having the same radius of curvature as the concave spherical surface on the lower surface of the base portion.

2. 2. The attachment structure for a reflux pipe in a lower vessel of a vacuum degassing apparatus according to claim 1, wherein the bottom of the lower vessel is formed by laying precast blocks.

3. 3. The attachment structure for a reflux pipe in a lower vessel of a vacuum degassing apparatus according to claim 1, wherein the reflux pipe is an integral part made of a precast block.

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