Dipping tube for molten steel treatment

Abstract

To provide a dipping tube which has a long service life and can be used over a long period of time without causing the falling off of an internal brick layer from a core metal even if molten metal enters from the boundary between an internal shaped refractory layer and a monolithic refractory during use, and without causing the molten metal to enter the joint surface with a reflux tube.SOLUTION: A dipping tube 1 has an inner shaped refractory layer 2 formed in a cylindrical shape by refractory brick, a metallic core metal 3, and an outer monolithic refractory layer 4 made of a monolithic refractory. A tapered portion 2b inclined inwardly from top to bottom is formed at the lower end of the outer periphery of the inner shaped refractory layer 2, a portion at the lower end of the core metal 3 is inclined inwardly from top to bottom so as to be parallel to the tapered portion 2b with a gap of a predetermined distance therebetween, and a gap G between the portion at the lower end of the core metal 3 and the tapered portion 2b of the inner shaped refractory layer 2 is filled with a monolithic refractory.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an immersion tube for treating molten steel, which is used in a vacuum degassing apparatus or the like. [Background technology]

[0002] In the secondary refining process of steelmaking, an immersion tube, the lower end of which is immersed in the molten steel in a ladle and through which molten steel flows, is attached to the lower end of a vacuum degassing apparatus and used. As disclosed in Patent Document 1, an immersion tube of this kind is known, which includes a cylindrical core metal along a vertical axis, a thick cylindrical brick layer (inner refractory layer) formed by assembling multiple bricks having a substantially rectangular parallelepiped shape (a prismatic shape with a trapezoidal or sector-shaped horizontal cross section) in multiple stages inside the core metal, and a thick cylindrical unshaped refractory layer formed on the outer periphery of the core metal by solidifying a flowable unshaped refractory material (castable, etc.).

[0003] Furthermore, in the immersion tube of Patent Document 1, in order to prevent the lower end of the monolithic refractory layer from falling off and the inner brick layer from falling off due to repeated heating and cooling during use, numerous recesses are provided on the back surface of the inner brick layer, and a flange-shaped support fitting is attached to the inside of the lower end of the core metal. Such an immersion tube is used by attaching it to the lower end of a vacuum degassing device with a reflux tube placed above and connected by fixing a joining flange provided at the lower end of the reflux tube to a joining flange provided at the upper end. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 10-259415 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the lower end of the immersion tube in Patent Document 1 is formed from amorphous refractory material, which has inferior heat resistance strength to shaped refractory material, and therefore, during use, the lower end portion made of amorphous refractory material may be dissolved by the molten steel flow, making it easier for heat to be transferred to the core metal, causing the core metal to deform and the internal brick layer (shaped refractory material) to wear off. To solve such problems, a structure in which the inner brick layer is extended to the bottom end is sometimes adopted, but when the inner brick layer is extended to the bottom end in this way, a material boundary between the inner brick layer and the outer monolithic refractory is created at the bottom end surface, and molten metal (molten iron) penetrates from the boundary (i.e., ingot insertion occurs), causing the core metal to melt or the core metal to deform due to the thermal load caused by the molten metal, which can result in the inner brick layer slipping down against the core metal and the molten metal sucked up from inside the ladle entering the joint surface with the reflux pipe (i.e., between the joint flange at the upper end and the joint flange of the reflux pipe). In other words, conventional immersion pipes such as those in Patent Document 1 were insufficient in preventing the inner brick layer from slipping down.

[0006] The object of the present invention is to provide an immersion tube for molten steel processing which eliminates the problems associated with the conventional immersion tubes described above, and which, even if molten metal infiltrates from the boundary between the internal molded refractory layer and the unshaped refractory layer during use, will not cause the internal brick layer to fall off from the core metal, will not allow molten metal to infiltrate into the joint surface with the reflux tube, and has a long service life and can be used for a long period of time. [Means for solving the problem]

[0007] Among the present invention, the invention described in claim 1 is an immersion tube for molten steel processing having a core metal formed into a cylindrical shape, an inner shaped refractory layer formed into a cylindrical shape from firebricks and provided on the inside of the core metal, and an outer amorphous refractory layer made of amorphous refractory provided so as to cover the outside of the core metal, wherein the inner shaped refractory layer reaches the lowest position, and a tapered portion sloping inward from top to bottom is formed at the lower end of the outer periphery of the inner shaped refractory layer, and the portion at the lower end of the core metal slopes inward from top to bottom so as to be parallel to the tapered portion of the inner shaped refractory layer with a gap of a predetermined distance between them, and the gap between the lower end of the core metal and the tapered portion of the inner shaped refractory layer is filled with the amorphous refractory that constitutes the outer amorphous refractory layer.

[0008] The invention described in claim 2 is characterized in that, in the invention described in claim 1, a circumferential groove is engraved in the tapered portion of the inner shaped refractory layer, and the inside of the groove is filled with the amorphous refractory that constitutes the outer amorphous refractory layer.

[0009] The invention described in claim 3 is characterized in that, in the invention described in claim 1, the gap between the lower end of the core bar and the tapered portion of the inner shaped refractory layer is adjusted to be 5 mm or more and 25 mm or less, and the inclination angle of the tapered portion of the inner shaped refractory layer relative to the vertical direction is adjusted to be 7° or more and less than 27°. Effect of the Invention

[0010] In the immersion tube described in claim 1, the lower end of the core metal is located outside the boundary between the inner shaped refractory layer and the outer unshaped refractory layer at a predetermined distance, and even if the metal (molten metal) penetrates from the boundary, the metal solidifies in the unshaped refractory before it seeps out to the core metal, so that the melting and deformation of the core metal can be effectively prevented. As a result, the immersion tube described in claim 1 can effectively suppress the falling off of the inner shaped refractory (shaped bricks, etc.) and the cracking and peeling damage of the outer unshaped refractory (castable, etc.), so that it can be used for a long period of time (i.e., it has a long life). In addition, the inclined portion that intrudes inward at the lower end of the core metal functions as a press that holds the inner shaped refractory layer that has been melted down from below, so that the falling off of the inner shaped refractory layer can be effectively prevented.

[0011] The immersion tube described in claim 2 has a long path (vertical path) from the lower end of the boundary between the inner shaped refractory layer and the outer unshaped refractory layer to the upper side, so that the molten metal that has entered from the boundary is unlikely to reach the upper side. Therefore, the immersion tube described in claim 2 can more effectively prevent the inner shaped refractory from falling off the outer unshaped refractory.

[0012] The immersion tube described in claim 3 has a gap (distance) between the lower end of the core wire and the tapered portion of the inner fixed refractory layer, and an inclination angle of the tapered portion of the inner fixed refractory layer with respect to the vertical direction adjusted to be within a predetermined numerical range, making it easy to carry out construction and maintenance for filling the gap with amorphous refractory material, and the inclined portion that extends inward at the lower end of the core wire can extremely effectively prevent the inner fixed refractory layer from falling off. [Brief description of the drawings]

[0013] [Figure 1] FIG. 2 is an explanatory diagram showing a dip tube (a is a front view, and b is a plan view). [Diagram 2] FIG. 2 is an explanatory diagram showing an immersion tube (a is a cross-sectional view taken along line AA in FIG. 1, and b is an enlarged view of a portion α in a). [Diagram 3]FIG. 2 is an explanatory diagram (vertical cross-sectional view) showing the use of the immersion tube. [Figure 4] FIG. 13 is an explanatory diagram (vertical cross-sectional view) showing a modified example of the inner shaped refractory layer. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, one embodiment of the immersion tube according to the present invention will be described in detail with reference to the drawings. <Dipping tube structure> 1 and 2 show an example of the immersion tube according to the present invention, and the immersion tube 1 is composed of an inner molded refractory layer 2, a core 3, and an outer unshaped refractory layer 4. The core 3 is formed into a cylindrical shape from a metal (steel) plate having a thickness of about 12.5 mm, and a constant diameter portion 3a having a height of about 240 mm and a constant diameter (about 780 mm) is provided in the central portion (the central portion in the height direction). In addition, an upper tapered portion 3b having a width of about 120 mm is connected to the upper side of the constant diameter portion 3a so that the diameter gradually increases toward the upper side. And, a flange (joint flange) 11 having a flat doughnut shape is fixed (welded) to the upper end of the upper tapered portion 3b so as to protrude outward from the outer periphery of the upper tapered portion 3b.

[0015] On the other hand, a lower tapered portion 3c having a width of about 130 mm is connected to the lower end of the constant diameter portion 3a of the core 3 so that the diameter gradually decreases toward the bottom. The lower tapered portion 3c is inclined at about 15° with respect to the vertical direction. In addition, a large number of anchors 10, 10..., each of which is made by bending a cylindrical steel rod into an approximately V-shape or an approximately Y-shape, are welded in a scattered manner to the outer circumferential surface (constant diameter portion 3a and lower tapered portion 3c) of the core 3. An inner shaped refractory layer 2 is concentrically arranged inside the core 3, and the lower end of the inner shaped refractory layer 2 reaches the lower end of the immersion tube 1.

[0016] The inner fixed refractory layer 2 has a constant diameter thick cylindrical constant diameter portion 2a formed on the upper side, and a cylindrical tapered portion 2b of a substantially inverted cone shape is connected to the lower side of the constant diameter portion 2a. A cylindrical molten metal flow path H of a constant diameter is formed in the center. The upper constant diameter portion 2a is formed into a thick cylindrical shape with a constant diameter (inner diameter = about 400 mm, outer diameter = about 700 mm) and a height of about 650 mm by assembling (fixing with mortar) a plurality of refractory bricks (refractories made of magnesia carbonaceous material) 5a, 5a... which are long in the height direction (vertical direction) (having the same height as the constant diameter portion 2a) and are substantially rectangular parallelepiped (prism-shaped with a trapezoid or fan-shaped horizontal cross section). The upper constant diameter portion 2a is formed into a thick cylindrical shape with a constant diameter (inner diameter = about 400 mm, outer diameter = about 700 mm) and a height of about 650 mm.

[0017] In addition, a tapered portion 2b with a height of about 200 mm is provided below the fixed diameter portion 2a so that the diameter gradually decreases toward the bottom. The tapered portion 2b, like the fixed diameter portion 2a, is formed by assembling (fixing with mortar) a plurality of approximately rectangular parallelepiped (prism-shaped with a trapezoid or fan-shaped horizontal cross section and an inclined outer peripheral surface) refractory bricks 5b, 5b, etc. that are long in the height direction (vertical direction) (having the same height as the tapered portion 2b) so that the upper and lower end positions do not shift. The tapered portion 2b is formed so that the thickness of the smallest diameter part at the bottom end is about 67% of the thickness of the fixed diameter portion 2a, and is inclined at about 15° with respect to the vertical direction.

[0018] In addition, two circumferential introduction grooves 7a, 7b are engraved on the outer periphery of the tapered portion 2b to increase (lengthen) the path (path in the vertical direction) from the lower end of the boundary between the inner shaped refractory layer 2 and the outer unshaped refractory layer 4 to the upper side. The lengths of the lower ends of the introduction grooves 7a, 7b and the lower end of the tapered portion 2b are 150 mm and 50 mm, respectively. The two introduction grooves 7a, 7b have the same shape, and the vertical cross section is substantially rectangular (i.e., a U-shaped cross section with substantially the same vertical width at the surface and the inner side), the vertical width is about 30 mm, and the depth (length from the surface to the inner side) is about 25 mm.

[0019] The inner shaped refractory layer 2 formed as described above is inserted inside the core metal 3 with a predetermined gap G therebetween, and the constant diameter portion 3a of the core metal 3 is arranged in parallel with the constant diameter portion 2a of the inner shaped refractory layer 2 at a distance of about 28 mm outside the constant diameter portion 2a of the inner shaped refractory layer 2. Furthermore, the lower tapered portion 3c of the core metal 3 is arranged in parallel with the tapered portion 2b of the inner shaped refractory layer 2 at a distance of about 20 mm outside the tapered portion 2b of the inner shaped refractory layer 2.

[0020] Meanwhile, on the outside of the inner fixed refractory layer 2 (including the inside and outside of the core metal 3), an outer monolithic refractory layer 4 is provided. The outer monolithic refractory layer 4 is formed by pouring (casting) castable (alumina-based castable), which is a flowable monolithic refractory, into a formwork that covers the core metal 3 with the inner fixed refractory layer 2 inserted therethrough, and then solidifying and drying it. The thickness between the outer periphery of the constant diameter portion 3a and the surface layer of the outer monolithic refractory layer 4 is about 100 mm.

[0021] Furthermore, the castable refractory constituting the outer monolithic refractory layer 4 is tightly filled in the gap G between the lower tapered portion 3c of the core metal 3 and the inner monolithic refractory layer 2, and is in a state of being inserted into two circumferential introduction grooves 7a, 7b provided in the tapered portion 2b of the inner monolithic refractory layer 2. The monolithic refractory that has entered the gap between the lower tapered portion 3c of the core metal 3 and the inner monolithic refractory layer 2, the monolithic refractory that has entered the introduction grooves 7a, 7b, and the monolithic refractory constituting the outer monolithic refractory layer 4 are integrated (continuous). Also, the lower end surface of the outer monolithic refractory layer 4 thus integrated is in a state of being flush with the lower end surface of the inner monolithic refractory layer 2 (the lower end surface of the immersion tube 1 itself).

[0022] <How to use the dip tube> Fig. 3 shows an example of a method of using the immersion tube 1 constructed as described above. The immersion tubes 1 are connected in pairs to a reflux tube C fixed to the lower end of the vacuum degassing apparatus 11, and are used with the lower end immersed in the molten metal (molten iron) S in a ladle 14. One of the two immersion tubes 1, 1 thus installed (immersion tube 1a on the left side of Fig. 3) functions as an ascending tube, and the other (immersion tube 1b on the right side of Fig. 3) functions as a descending tube. In the vacuum degassing apparatus 11, the upper vessel 12 and the lower vessel 13 are evacuated and an inert gas (such as argon gas) is blown into the immersion tube 1a, which is an ascending pipe, via piping. The molten metal in the ladle 14 is drawn into the lower vessel 13 and rises through the molten metal passage (inside the inner shaped refractory layer 2) of the immersion tube 1a, which is an ascending pipe, and then descends through the molten metal passage of the immersion tube 1b, which is a downcomer pipe, and circulates back to the ladle 14. During this circulating process, the molten metal is degassed and discharged to the outside of the vacuum degassing apparatus 11.

[0023] When the immersion tubes 1a, 1b are mounted in the vacuum degassing apparatus 11 as described above and degassed, it is possible that the molten metal may enter through the boundary between the inner fixed refractory layer 2 and the outer unshaped refractory layer 4. However, at the lower end of the inner fixed refractory layer 2 of the immersion tubes 1a, 1b, a gap G of a certain width is formed between the tapered portion 2b and the lower tapered portion 3c of the core 3, and this gap G is filled with the unshaped refractory that constitutes the outer unshaped refractory layer 4, so that it is highly unlikely that the molten metal that has entered through the boundary will reach the core 3 or that the temperature of the core will rise sharply due to the heat of the molten metal.

[0024] In addition, two circumferential introduction grooves 7a, 7b are formed in the tapered portion 2b of the inner shaped refractory layer 2 of the immersion tubes 1a, 1b, and the path (vertical path) from the lower end of the boundary between the inner shaped refractory layer 2 and the outer unshaped refractory layer 4 to the upper portion is long, so that the molten metal that has entered from the lower end of the boundary is unlikely to reach the upper portion. Therefore, in the immersion tubes 1a, 1b, the inner shaped refractory layer 2 is unlikely to slip off the outer unshaped refractory layer 4. Furthermore, even if the inner shaped refractory layer 2 does slip off the outer unshaped refractory layer 4, the lower end of the inner shaped refractory layer 2 is received by the lower tapered portion 3c that has entered the inside of the core metal 3, so that the inner shaped refractory layer 2 does not fall off the outer unshaped refractory layer 4.

[0025] <Effect of the dip tube> As described above, the immersion tube 1 has an inner fixed refractory layer that reaches the lowest position, and a tapered portion 2b that slopes inward from top to bottom is formed at the lower end of the outer periphery of the inner fixed refractory layer 2, and the portion at the lower end of the core metal 3 slopes inward from top to bottom so as to be parallel to the tapered portion 2b of the inner fixed refractory layer 2 with a predetermined distance (approximately 20 mm) between it and the tapered portion 2b of the inner fixed refractory layer 2, and the gap G between the lower end of the core metal 3 and the tapered portion 2b of the inner fixed refractory layer 2 is filled with the fixed refractory that constitutes the outer fixed refractory layer 4. That is, the lower end of the metal core 3 of the immersion tube 1 is located outside and at a predetermined distance from the boundary between the inner monolithic refractory layer 2 and the outer monolithic refractory layer 4, so that even if molten metal intrudes from the boundary, the molten metal solidifies within the monolithic refractory before seeping out to the metal core 3, effectively preventing melting and deformation of the metal core 3. As a result, the immersion tube 1 can effectively prevent the inner monolithic refractory 2 (i.e., the monolithic bricks 5a, 5b) from falling off and the outer monolithic refractory 4 (castable, etc.) from cracking and peeling, allowing it to be used for a long period of time (i.e., has a long life).

[0026] In addition, the immersion tube 1 has circumferential introduction grooves 7a, 7b engraved in the tapered portion 2b of the inner monolithic refractory layer 2, and the introduction grooves 7a, 7b are filled with the monolithic refractory constituting the outer monolithic refractory layer 4, so that the path (vertical path) from the lower end of the boundary between the inner monolithic refractory layer 2 and the outer monolithic refractory layer 4 to the upper side is long, making it difficult for the molten metal that has entered from the boundary to reach the upper side. Therefore, the immersion tube 1 can more effectively prevent the inner monolithic refractory 2 from falling out of the outer monolithic refractory 4.

[0027] Furthermore, the gap G between the lower end of the core 3 and the tapered portion 2b of the inner fixed refractory layer 2 of the immersion tube 1 is adjusted to 20 mm, and the inclination angle of the tapered portion 2b of the inner fixed refractory layer 2 with respect to the vertical direction is adjusted to 15°, making it easy to carry out construction and maintenance work to fill the gap G with amorphous refractory material, and the lower tapered portion 3c that extends inward from the lower end of the core 3 functions as a clamp to support the inner fixed refractory 2 from below, thereby extremely effectively preventing the inner fixed refractory layer 2 from falling off.

[0028] <Example of changing the dip tube> The immersion tube of the present invention is not limited to the above-mentioned embodiment, and the materials, shapes, structures, sizes, etc. of the inner shaped refractory layer, core wire, outer unshaped refractory layer, etc. can be appropriately modified as necessary within the scope of the spirit of the present invention.

[0029] For example, the outer amorphous refractory layer is not limited to being formed from an alumina-based castable as in the above embodiment, but may be changed to being formed from a castable other than alumina castable, such as an alumina-magnesia-based castable. Also, the outer amorphous refractory layer is not limited to being formed from a single type of amorphous refractory as in the above embodiment, but may be formed from a plurality of types of amorphous refractories, such as one in which the portion in contact with the introduction groove is formed from an alumina-based castable and the other portions (such as the outer periphery and lower end of the core metal) are formed from an alumina-magnesia-based castable.

[0030] In addition, the inner shaped refractory layer is not limited to being formed by assembling refractory bricks made of magnesia-carbon material as in the above embodiment, but may be changed to being formed by assembling refractory bricks made of various acidic refractories, neutral refractories, basic refractories, etc. other than magnesia-carbon material, such as refractory bricks made of magnesia-chrome material or refractory bricks made of silicon carbide material. Note that when the inner shaped refractory layer is formed by assembling refractory bricks made of basic refractories mainly composed of magnesia-carbon material or magnesia-chrome material, it is preferable because the inner shaped refractory layer has good resistance to melting damage by molten steel and therefore has better performance of preventing the inner shaped refractory layer from falling off the immersion tube.

[0031] In addition, the circumferential introduction groove provided on the outer periphery of the tapered portion of the inner shaped refractory layer is not limited to a rectangular cross section as in the above embodiment, but may be changed to a trapezoidal cross section, an inverted trapezoidal cross section (so-called dovetail groove shape), a U-shaped cross section (sideways U-shaped), etc. Furthermore, even when an introduction groove having a rectangular cross section is provided, the size of the introduction groove is not limited to the size (vertical width = 30 mm × depth (depth from the surface to the back side) = 25 mm) as in the above embodiment, but may be appropriately changed as necessary within the range of a vertical width of 20 to 50 mm and a depth of 10 to 30 mm.

[0032] In addition, the inner shaped refractory layer is not limited to the one having two circumferential introduction grooves on the outer periphery of the tapered portion as in the above embodiment, but may be changed to one having a single circumferential introduction groove or one having three or more circumferential introduction grooves. Note that the shape and number of the circumferential introduction grooves need to be appropriately adjusted depending on the weight of the inner shaped refractory layer, etc.

[0033] In addition, the tapered portion of the inner shaped refractory layer is not limited to the above embodiment, in which the thickness of the smallest diameter portion is about 67% of the thickness of the constant diameter portion, and the shape can be appropriately changed as necessary. It is preferable to form the tapered portion of the inner shaped refractory layer so that the thickness of the smallest diameter portion is 50% (1 / 2) to 75% (3 / 4) of the thickness of the constant diameter portion, since this prevents the structural strength from being extremely reduced.

[0034] Furthermore, when the tapered portion of the inner shaped refractory layer is formed so that the thickness of the smallest diameter portion is about 50% (50-55%) of the thickness of the constant diameter portion as shown in Fig. 4(a), it is preferable to set the inclination angle θ of the tapered portion to the vertical direction to 7° or more and less than 14° and to set the lower tapered portion of the core metal to be inclined at the same angle, since this prevents the structural strength of the tapered portion from being extremely reduced and improves the function of preventing the inner shaped refractory layer from falling off due to the core metal. On the other hand, when the tapered portion of the inner shaped refractory layer is formed so that the thickness of the smallest diameter portion is about 75% (70-75%) of the thickness of the constant diameter portion as shown in Fig. 4(b), it is preferable to set the inclination angle θ of the tapered portion to the vertical direction to 14° or more and less than 27° and to set the lower tapered portion of the core metal to be inclined at the same angle, since this improves the function of preventing the inner shaped refractory layer from falling off due to the core metal. Furthermore, it is particularly preferable to form the thickness of the smallest diameter part to be approximately 60 to 70% of the thickness of the constant diameter part, set the inclination angle θ of the tapered part relative to the vertical direction to be 13° or more and 17° or less, and make the lower tapered part of the core wire inclined at the same angle, as this provides an extremely good function of preventing the inner shaped refractory layer from falling off.

[0035] In addition, the immersion tube according to the present invention is not limited to the above embodiment in which the gap between the tapered portion of the inner fixed refractory layer and the lower tapered portion of the core is adjusted to about 20 mm, and the gap can be appropriately changed as necessary within the range of 5 mm to 30 mm. If the gap is less than 5 mm, it is not preferable because it is difficult to fill the amorphous refractory when forming the outer amorphous refractory layer outside the inner fixed refractory layer (workability is deteriorated). On the other hand, if the gap exceeds 30 mm, in the event that the inner fixed refractory layer that has melted and slipped off the outer amorphous refractory layer, the lower end of the inner fixed refractory layer cannot be received by the lower tapered portion of the core, and it is not preferable because it is not possible to prevent the inner fixed refractory layer from falling off. It is more preferable that the gap between the tapered portion of the inner fixed refractory layer and the lower tapered portion of the core is 10 mm to 25 mm.

[0036] Furthermore, in order to increase the retention strength of the outer unshaped refractory layer, the core is not limited to a V- or Y-shaped metal stud (a round bar or the like bent into a V- or Y-shape) fixed (welded or screwed with a bolt or the like) to the outer periphery of the lower side (constant diameter section and lower tapered section) as in the above embodiment, but may be a metal stud having a shape different from a V- or Y-shape, such as a cross shape or a bolt shape, fixed to the outer periphery of the lower side. In addition, the core can be changed to a metal ring body (round bar or the like) wound around the outer periphery of the lower end of the lower tapered section to prevent the lower end of the lower tapered section from opening due to thermal load. [Industrial Applicability]

[0037] Since the immersion tube of the present invention has the excellent effects as described above, it can be suitably used as a component that is attached to a vacuum degassing apparatus and functions as an ascending pipe or a descending pipe during secondary refining of molten steel. [Explanation of symbols]

[0038] 1...dip tube 2 Inner shaped refractory layer 2b Tapered section 3. Core wire 3c Lower tapered section (tapered section) 4.Outer monolithic refractory layer 7a,7b...Introduction groove 11. Vacuum degassing equipment

Claims

1. An immersion tube for molten steel treatment, comprising: a core metal formed into a cylindrical shape from a metal; an inner shaped refractory layer formed into a cylindrical shape from firebricks and provided on the inside of the core metal; and an outer unshaped refractory layer made of unshaped refractory material and provided so as to cover the outside of the core metal, The inner shaped refractory layer reaches the lowest position, and a tapered portion inclined inwardly from above to below is formed at the lower end of the outer periphery of the inner shaped refractory layer, a portion of the lower end of the core metal is inclined inwardly from above to below so as to be parallel to the tapered portion of the inner shaped refractory layer with a gap of a predetermined distance therebetween; An immersion pipe for molten steel processing, characterized in that the gap between the lower end of the core metal and the tapered portion of the inner shaped refractory layer is filled with amorphous refractory material that constitutes the outer amorphous refractory layer.

2. An immersion pipe for molten steel treatment as described in claim 1, characterized in that a circumferential groove is engraved in the tapered portion of the inner shaped refractory layer, and the inside of the groove is filled with the amorphous refractory that constitutes the outer amorphous refractory layer.

3. The gap between the lower end of the core metal and the tapered portion of the inner shaped refractory layer is adjusted to 5 mm or more and 25 mm or less, 2. The immersion pipe for molten steel treatment according to claim 1, characterized in that the inclination angle of the tapered portion of the inner shaped refractory layer with respect to the vertical direction is adjusted to be equal to or greater than 7° and less than 27°.

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