JP6545869B1 - Dip tube - Google Patents

Abstract

A dip tube in which damage due to intrusion of molten metal is suppressed is provided. A dip tube 1 of the present invention has a cylindrical core metal 2 and a peripheral brick formed in a cylindrical shape composed of a plurality of bricks 33 arranged side by side along the outer peripheral surface of the core metal 2. In the dip tube 1 having the layer 30 and at least the castable layer 32 disposed on the lower side of the core metal 2, the castable layer 32 is formed so as to cover the lower end portion of the outer peripheral surface of the outer peripheral brick layer 30. It is characterized by In the immersion tube 1 of the present invention, the radially outer end of the interface between the lower end surface 30 a of the outer peripheral brick layer 30 and the castable layer 32 is covered with the castable layer 32. As a result, in the immersion tube 1 of the present invention, the penetration of the molten metal 43 into the interface between the lower end face 30 a of the outer peripheral brick layer 30 and the castable layer 32 is suppressed, and the damage of the immersion tube 1 due to the intrusion of the molten metal 43 is suppressed. [Selected figure] Figure 1

Description

  The present invention relates to a dip tube.

  DESCRIPTION OF RELATED ART Conventionally, the immersion pipe | tube used for a vacuum degassing apparatus etc. is known (for example, refer patent document 1). The immersion pipe comprises a cylindrical core metal, a cylindrical inner peripheral brick layer arranged on the inner peripheral side of the core metal, and a cylindrical outer peripheral shaped brick arranged on the outer peripheral side of the core metal. An outer peripheral brick layer and a castable layer disposed at least below the core metal are provided. In the dip tube, a molten metal passage, through which the molten metal flows, is formed inside the cylindrical core metal.

  The dip tube is used by immersing the lower end (in particular, the lower portion of the castable layer) in the molten metal in the ladle. In this immersion tube, in use, the molten metal flows from the lower side toward the upper side of the molten metal passage or from the upper side to the lower side while the lower portion of the castable layer is immersed in the high temperature molten metal in the ladle.

In the immersion pipe described in Patent Document 1, a step is formed at the lower end portion of the outer peripheral brick layer by alternately arranging a fixed short brick and a fixed long brick in the circumferential direction. Is configured. Further, the castable layer is formed to bite into the step of the outer peripheral side brick layer. Furthermore, the outer peripheral side brick layer and the castable layer are formed in the state where the outer peripheral surface is in the same plane (in the state where there is no level difference in the outer peripheral surface).
According to this conventional immersion tube, it is possible to suppress the melting loss in the slag line by the outer peripheral brick layer made of the outer peripheral portion shaped brick.

JP 10-219340 A

However, in the conventional immersion pipe, the castable layer is formed under the outer peripheral brick layer, and the molten metal may intrude into the boundary between the outer peripheral brick layer and the castable layer to damage the immersion pipe. .
Specifically, in the conventional immersion tube described in Patent Document 1, long bricks and short bricks are alternately arranged in the circumferential direction, and the lower end of the outer peripheral brick layer has an uneven shape in the circumferential direction. There is. Each of the long brick and the short brick has a flat interface surface and a lower end surface. The outer diameter side end of each of the long brick and the short brick is connected to the outer peripheral surface of the immersion pipe. And this immersion pipe is used by immersing in the molten metal so that the slag line may overlap with the outer peripheral side brick layer at the lower end. Then, the outer diameter end of the boundary between the lower end surface of the outer peripheral brick layer and the upper end surface of the castable layer is located in the molten metal, and the molten metal intrudes into this boundary. The boundary forms a substantially flat surface, and when the molten metal intrudes into the boundary, the molten metal permeates along the substantially planar boundary to the inner diameter side, and reaches a metal fitting for fixing the outer peripheral shaped brick of the outer peripheral brick layer. Then, the molten metal melts the metal fitting, and as a result, the castable layer falls off. When melting further progresses, there is also a possibility that the outer peripheral shaped brick of the outer peripheral side brick layer may fall off.

  The present invention has been made in view of the above situation, and an object of the present invention is to provide a dip tube in which damage due to penetration of molten metal is suppressed.

The immersion pipe according to the present invention for solving the above problems comprises: a cylindrical core metal; and an outer peripheral brick layer formed in a cylindrical shape comprising a plurality of bricks arranged side by side along the outer peripheral surface of the core metal; In the immersion tube having at least a castable layer disposed on the lower side of the core, the castable layer covers the lower end portion of the outer peripheral surface of the outer peripheral brick layer, and the outer peripheral surface of the outer peripheral brick layer is exposed at the upper portion thereof It is characterized in that it is formed to

  In the immersion tube of the present invention, the castable layer is formed to cover the lower end of the outer peripheral surface of the outer peripheral brick layer, and the radially outer end of the interface between the lower end surface of the outer peripheral brick layer and the castable layer is , Covered with castable layer. As a result, penetration of the molten metal to the interface between the lower end surface of the outer peripheral brick layer and the castable layer is suppressed, and damage to the immersion pipe due to the penetration of the molten metal is suppressed.

Further, the outer diameter side end of the boundary between the outer peripheral brick layer and the castable layer is located on the outer peripheral surface of the outer peripheral brick layer. Then, even if the molten metal intrudes into this end, the molten metal penetrates downward along the outer peripheral surface of the outer peripheral brick layer, and the molten metal hardly reaches the boundary with the lower end surface of the outer peripheral brick layer .
In the immersion pipe according to the present invention, of the both ends in the axial direction, the end portion side to be immersed in the molten metal is the lower side in the vertical direction, and the opposite end side is the upper side in the vertical direction.

FIG. 2 is a cross-sectional view showing the configuration of the immersion pipe of Embodiment 1; It is an expanded view when the lower end of the immersion pipe | tube of Embodiment 1 is seen from radial direction outer side. FIG. 2 is a cross-sectional view showing the vicinity of the covering portion of the immersion tube of the first embodiment. BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing which shows the structure of the vacuum degassing apparatus using the immersion pipe | tube of Embodiment 1. FIG. It is sectional drawing which shows the coating | coated part vicinity of the immersion pipe | tube of Embodiment 2. FIG. It is sectional drawing which shows the coating | coated part vicinity of the immersion pipe | tube of Embodiment 3. FIG. It is sectional drawing which shows the coating | coated part vicinity of the immersion pipe | tube of Embodiment 4. FIG. It is sectional drawing which shows the coating | coated part vicinity of the immersion pipe | tube of each Example and each comparative example.

Hereinafter, the immersion tube of the present invention will be specifically described using the embodiment.
Embodiment 1
The present embodiment is a dip tube whose configuration is shown in FIGS. 1 to 3. The immersion tube 1 of the present embodiment has a core metal 2 and a refractory layer 3.

  The cored bar 2 has a cored bar main body 20, brick press hardwares 21 and 22, and studs 23. The core metal 2 is made of a metal material (for example, an iron-based metal such as carbon steel or alloy steel, preferably a heat-resistant metal). The metal material which comprises the metal core 2 may be either the same metal material as the metal core body 20 and the brick holding members 21 and 22, or different metal materials. The metal core body 20 and the brick holding members 21 and 22 are joined by welding.

  The cored bar main body 20 is formed in a cylindrical shape which is continuous in the circumferential direction. The cored bar 2 functions as a core body of the refractory layer 3 and has an outside air blocking function to prevent the outside air existing on the outer peripheral side of the immersion tube 1 from infiltrating into the below-described molten metal passage.

  The brick pressing fitting 21 is provided integrally with the lower portion (lower end) of the core metal main body 20 so as to protrude radially outward and upward from the outer peripheral surface of the core metal main body 20. That is, the brick holding member 21 is formed in a substantially conical shape with the upper part opened as a whole. The brick holding member 21 has a shape in which the upper surface 21 b corresponds to a radially inward portion of the end surface 30 a of the lower end of the outer brick layer 30. The brick pressing fitting 21 has a shape corresponding to a step described later provided along the circumferential direction. The radially outward protrusion amount of the brick pressing fitting 21 is shorter than the thickness of the outer brick layer 30. That is, the brick pressing fitting 21 is provided so as to be embedded in the castable layer 32 without being exposed to the outer peripheral surface.

  The brick holding member 22 is provided integrally with the lower portion (lower end) of the metal core body 20 so as to protrude radially inward from the inner peripheral surface of the metal core body 20 (that is, in the axial center direction of the metal core body 20) There is. The brick pressing fitting 22 has a shape in which the upper surface 22 b corresponds to the radially inward portion of the end surface 31 a of the lower end of the inner brick layer 31. The brick pressing fitting 22 of the present embodiment has a substantially annular plate shape as a whole. The brick pressing fitting 22 has a shape corresponding to a step described later provided along the circumferential direction. The radially inward protrusion amount of the brick pressing fitting 22 is shorter than the thickness of the inner brick layer 31. That is, the brick pressing fitting 21 is provided so as to be embedded in the castable layer 32 without being exposed to the inner peripheral surface.

  The studs 23 are integrally fixed (joined) to the lower portion (lower end) of the cored bar main body 20, and extend in the radial direction or the axial direction. The studs 23 are formed by processing a wire made of heat-resistant metal into a V-shape or a Y-shape. A plurality of studs 23 are provided over the entire circumference at predetermined intervals in the circumferential direction of the cored bar main body 20. Fixing of the studs 23 to the metal core body 20 is realized by, for example, welding or bolts. The studs 23 have a function of preventing the castable layer 32 from falling off.

  The refractory layer 3 has an outer brick layer 30, an inner brick layer 31, and a castable layer 32. The outer brick layer 30 and the inner brick layer 31 are respectively formed of magnesia carbon or a magnesia chromium refractory (fire brick 33, 34) fired at a high temperature. This refractory is a fired body and has high heat resistance and high strength. Each of the outer brick layer 30 and the inner brick layer 31 may be formed of the refractory bricks 33, 34 of the same material, or may be formed of the refractory bricks 33, 34 of different materials. In this embodiment, the same magnesia-carbon refractory bricks 33 and 34 are formed.

  The outer brick layer 30 is composed of a plurality of refractory bricks 33 arranged along the outer peripheral surface of the cored bar main body 20 of the cored bar 2 and has a tubular shape as a whole. The outer brick layer 30 is formed by arranging a plurality of firebricks 33 in the circumferential direction without gaps. The castable layer 35 is provided between the outer brick layer 30 and the outer peripheral surface of the cored bar main body 20 of the cored bar 2.

The outer brick layer 30 is flat so that the upper end position of the refractory brick 33 located at the upper end of the outer brick layer 30 does not shift over the entire circumference in use, that is, the axial end face is horizontal all around (A plane perpendicular to the axial direction of 1).
The outer brick layer 30 is configured such that the lower end position of the refractory brick 33 located at the lower end of the outer brick layer 30 is displaced in the circumferential direction during use, that is, the other end face 30a in the axial direction is not flat all around It is done.

  At the lower end portion of the outer brick layer 30 in use, there is formed a step whose lower end position changes in the circumferential direction. That is, the outer brick layer 30 has the level | step difference which the lower end position of the firebrick 33 located in the lower end and adjacent to the circumferential direction shifted | deviated to the axial direction. The plurality of firebricks 33 aligned in the circumferential direction in the outer brick layer 30 are configured by long long bricks 33A of axial length and short bricks 33B of short axial length. The step is formed by alternately arranging the long bricks 33A and the short bricks 33B in the circumferential direction.

  The outer brick layer 30 is a surface which spreads at an angle with respect to the horizontal direction, and the end surface 33a of the lower end of each of the refractory bricks 33 is formed such that the normal thereof is directed radially outward. That is, the outer peripheral brick layer 30 has a shape in which the end face of the lower end is inclined with respect to the vertical direction (axial direction) and the horizontal direction (direction perpendicular to the axial direction) so that the outer diameter decreases as going downward. I am

  In the present embodiment, the outer brick layer 30 is formed to have a length in the vertical direction (axial direction) of 430 mm for the long brick 33A and 400 mm for the short brick 33B. The end face 33a of the lower end of the refractory brick 33 has a length of 55 mm (13% of the length of the outer brick layer 30) in the vertical direction (axial direction). The radial thickness is 75 mm.

  The inner brick layer 31 is composed of a plurality of firebricks 34 arranged along the inner peripheral surface of the cored bar main body 20 of the cored bar 2 and has a tubular shape as a whole. A molten metal passage through which the molten metal 43 flows is formed on the inner diameter side of the inner brick layer 31 (that is, the cylindrical shaft core portion). The inner brick layer 31 is formed by arranging a plurality of firebricks 34 in the circumferential direction without gaps. The castable layer 36 is provided between the inner brick layer 31 and the inner peripheral surface of the cored bar main body 20 of the cored bar 2.

The inner brick layer 31 is flat so that the upper end position of the firebrick 34 located at the upper end of the inner brick layer 31 does not shift over the entire circumference in use, that is, the one end face in the axial direction is horizontal all around (A plane perpendicular to the axial direction of 1).
The inner brick layer 31 is configured such that the lower end position of the refractory brick 34 located at the lower end of the inner brick layer 31 in use is displaced in the circumferential direction, that is, the other end face in the axial direction is not flat all around ing.
The inner brick layer 31 is formed such that the end surface 34a of the lower end of each of the refractory bricks 34 has a surface extending in the horizontal direction.

At the lower end portion of the inner brick layer 31 in use, like the outer brick layer 30, there is formed a step whose lower end position changes in the circumferential direction. That is, the inner brick layer 31 has the level | step difference which the lower end position of the firebrick 34 located in a lower end and adjacent to the circumferential direction shifted mutually in the axial direction. The plurality of refractory bricks 34 aligned in the circumferential direction in the inner brick layer 31 are configured of long long bricks 34A with an axial length and short short bricks 34B with a short axial length. The step is formed by alternately arranging the long bricks 34A and the short bricks 34B in the circumferential direction.
The lower end of the outer brick layer 30 is formed in a shape in which unevenness is repeated in the circumferential direction corresponding to the lower ends of the long bricks 33A and the short bricks 33B, as shown in FIG. It is done.

  The lower end surfaces of the brick layers 30 and 31 are in contact with the brick holding members 21 and 22 and in contact with the upper surface of the castable layer 32. The castable layer 32 is formed to bite into the steps of the respective brick layers 30 and 31, and is configured such that a step whose upper end position changes in the circumferential direction is formed in accordance with the step.

  The castable layer 32 is disposed below the outer brick layer 30 and the inner brick layer 31. The castable layer 32 is a member provided at the lower part of the immersion pipe 1 which is immersed in the molten metal 43 when the lower end of the immersion pipe 1 is immersed in the molten metal 43.

The castable layer 32 is made of a relatively refractory material that can withstand the temperature of the molten metal 43. The material of the castable layer 32 is, for example, an alumina-based material having a purity of 90% by mass or more of alumina, or a material of alumina magnesia, alumina spinel, or alumina magnesia spinel.
The castable layer 32 has a predetermined cavity shape, and can be formed by pouring a flowable material (for example, powder) into a mold in which the lower portion of the core metal 2 is held.
The castable layer 32 is embedded so as not to expose the lower portion of the cored bar 2 (the cored bar main body 20, the brick pressing hardwares 21, 22 and the studs 23). That is, the lower part of the core metal 2 does not contact the molten metal 43.

  The castable layer 32 has a substantially cylindrical shape as a whole, and an axial center portion thereof defines a molten metal passage through which the molten metal 43 flows. The molten metal passage is in communication with the molten metal passage defined in the inner brick layer 31. The molten metal passage has a diameter that matches the diameter of the molten metal passage. That is, the inner diameter of the cylindrical inner brick layer 31 and the inner diameter of the cylindrical castable layer 32 coincide with each other. That is, the molten metal passage of the immersion pipe is formed without changing the diameter.

As shown in the enlarged cross-sectional view of FIG. 3, a cylindrical outer diameter upper end of the castable layer 32 is formed with a covering portion 37 that covers the lower end portion of the outer peripheral surface of the outer brick layer 30. That is, the castable layer 32 is formed such that the cylindrical outer peripheral surface has a diameter larger than that of the outer peripheral surface of the outer brick layer 30. The upper end of the outer peripheral surface of the castable layer 32 is formed above the lower end of the outer peripheral surface of the outer brick layer 30.
As shown in FIG. 3, the covering portion 37 of the castable layer 32 is formed such that the upper surface 37b thereof forms an inclined surface. The inclined surface of the upper surface 37b of the covering portion 37 is formed to descend as advancing radially outward.

  The radial thickness of the covering portion 37 of the castable layer 32 (that is, the difference between the outer diameter of the castable layer 32 and the outer diameter of the outer brick layer 30) is preferably 10 to 20 mm. When the thickness of the covering portion 37 is 10 mm or more, the effect of forming the covering portion 37 can be sufficiently exhibited. If it exceeds 20 mm, inclusions (e.g., slag) of the molten metal 43 adhere to the upper surface of the covering portion 37 to cause the covering portion 37 to peel off.

  The length in the vertical direction (axial direction of the immersion tube 1) of the covering portion 37 of the castable layer 32 is not limited. For example, setting it as 10 mm or more, 20 mm or more, 30 mm or more, 40 mm or more, 50 mm or more can be mentioned. The length of the covering portion 37 in the vertical direction is preferably 50 mm or more. That is, it is more preferable that the length of the coating | coated part 37 in the outer peripheral surface of the short brick 33B is 50 mm or more. The length in the vertical direction of the covering portion 37 is preferably 50 to 200 mm, and more preferably 100 to 150 mm. The length of the covering portion 37 indicates the length from the upper end portion of the step at the lower end portion of the outer peripheral surface of the outer peripheral brick layer 30. When the length of the covering portion 37 is 50 mm or more, the occurrence of melting loss can be particularly suppressed, and when it exceeds 200 mm, the length covering the outer brick layer 30 becomes excessively long, and the outer brick layer 30 is provided. It becomes difficult for the effects of

(Vacuum degassing device)
The immersion tube 1 of this embodiment is used, for example, in the vacuum degassing apparatus 4 shown in FIG.
The vacuum degassing apparatus 4 degasses hydrogen gas (H ₂ gas), oxygen gas (O ₂ gas) and the like from the molten metal 43 by refluxing the molten metal 43 such as molten steel under vacuum. It is.

The vacuum degassing apparatus 4 includes an upper tank 40, a lower tank 41, and a pair of two immersion tubes 1.
The upper tank 40 is depressurized to a high vacuum state. The lower tank 41 is in communication with the upper tank 40 below the upper tank 40. The pair of immersion tubes are respectively communicated with the lower tank 41 below the lower tank 41 and immersed in the molten metal 43 in the ladle 42. The pair of immersion tubes are arranged side by side. One immersion pipe 1 (left side in FIG. 4) is a rising pipe 1a in which the molten metal 43 rises, and the other immersion pipe 1 (right side in FIG. 4) is a descending pipe 1b in which the molten metal 43 descends.

In the vacuum degassing apparatus 4 having the above-described structure, an inert gas (for example, argon gas or the like) is blown into the uprising pipe 1a through a pipe (not shown) during use, that is, during operation. When inert gas is blown into the rising pipe 1a, the molten metal 43 in the ladle 42 is drawn toward the lower tank 41 due to the vacuum state of the upper tank 40 and ascends the molten metal passage of the rising pipe 1a. The molten metal passage 1b is lowered and returned to the ladle 42 to be circulated. In the process of the reflux, degassing of the molten metal 43 proceeds and the gas is discharged to the outside of the vacuum degassing apparatus 4.
In the vacuum degassing apparatus 4, the castable layer 32 is completely immersed in the molten metal 43 until the immersion pipe 1 (the rising pipe 1 a and the descending pipe 1 b) overlaps the outer brick layer 30 and the slag line of the molten metal 43. The lower end of the immersion tube 1 is immersed in the molten metal 43 to the position.

(Effect of this form)
According to this embodiment, the immersion pipe 1 has the core metal 2, the outer peripheral brick layer 30 and the castable layer 32, and the castable layer 32 is formed to cover the lower end portion of the outer peripheral surface of the outer peripheral brick layer 30. That is, the castable layer 32 has the covering portion 37.

  According to this configuration, the radially outward end of the interface between the end face 30a of the lower end of the outer peripheral brick layer 30 and the castable layer 32 is covered with the covering portion 37 of the castable layer 32 and the lower end of the immersion pipe 1 Even when immersed in the molten metal 43, the interface between the end surface 30 a at the lower end of the outer peripheral brick layer 30 and the castable layer 32 is not exposed to the molten metal 43. For this reason, the penetration of the molten metal 43 into the interface between the end surface 30a of the lower end of the outer peripheral brick layer 30 and the castable layer 32 is suppressed, and the damage of the immersion pipe 1 due to the penetration of the molten metal 43 is suppressed.

  Further, the outer diameter side end of the interface between the outer peripheral brick layer 30 and the castable layer 32 is located on the outer peripheral surface of the outer peripheral brick layer 30. Then, even if the molten metal 43 intrudes into the end of this boundary, the molten metal 43 infiltrates downward along the outer peripheral surface of the outer peripheral brick layer 30, and the molten metal 43 is in the end face 30a of the lower end of the outer peripheral brick layer 30. It is difficult to reach. Also from this, damage to the immersion pipe 1 due to the penetration of the molten metal 43 can be suppressed.

  According to this embodiment, the castable layer 32 covers the lower end portion of the outer peripheral surface of the outer peripheral brick layer 30 with a length of 50 to 200 mm. That is, the covering portion 37 is formed to have a length of 50 to 200 mm. According to this configuration, the castable layer 32 can sufficiently exhibit the effect of covering the radially outward end of the interface between the end surface 30 a of the lower end of the outer peripheral brick layer 30 and the castable layer 32.

According to this embodiment, the firebrick 33 forming the outer peripheral brick layer 30 is made of magnesia carbon. According to this configuration, the inclusions (for example, slag contained in the molten metal 43) present in the molten metal 43 are less likely to adhere to the outer peripheral brick layer 30. Moreover, even if the inclusions adhere to the outer peripheral brick layer 30, the attached matter can be peeled off by mechanical impact.
When inclusions adhere to the castable layer 32, it is necessary to remove the attached inclusions from the castable layer 32 (the need for removing the glue). When the inclusions are removed from the castable layer 32, the inclusions cause exfoliation of the castable to form the castable layer 32.
In this embodiment, the outer brick layer 30 made of the magnesia-carbon refractory brick 33 is provided on the outer peripheral side of the refractory layer 3, and adhesion of inclusions to the refractory brick 33 is suppressed. As a result, it is easy to remove the attached inclusions (slough removal operation), and it is possible to reduce the time and cost required for maintenance (i.e., the removal of the residue and repair of the castable layer 32).

Second Embodiment
The present embodiment is the same immersion tube 1 as the first embodiment except that the configuration in the vicinity of the lower end portion of the outer brick layer 30 is different. The configuration in the vicinity of the lower end portion of the outer brick layer 30 of the immersion pipe 1 of the present embodiment is shown in FIG. 5 in an enlarged sectional view.
In the immersion tube 1 according to the present embodiment, as shown in FIG. 5, the end face 30 a of the lower end of the outer brick layer 30 is in the same direction as the end face 31 a of the lower end of the inner brick layer 31. It is formed to spread out.
Also in the immersion tube 1 of the present embodiment, the radially outer end of the interface between the end surface 30 a of the lower end of the outer peripheral brick layer 30 and the castable layer 32 is covered with the covering portion 37 of the castable layer 32. It exerts the same effect as

Third Embodiment
The present embodiment is the same immersion tube 1 as the first embodiment except that the configuration in the vicinity of the lower end portion of the outer brick layer 30 is different. The configuration in the vicinity of the lower end portion of the outer brick layer 30 of the immersion pipe 1 of the present embodiment is shown in FIG. 6 in an enlarged sectional view.
As shown in FIG. 6, the immersion tube 1 of the present embodiment is formed such that the diameter in the vicinity of the lower end portion of the outer peripheral surface of the outer brick layer 30 is reduced. And the covering part 37 of the castable layer 32 is formed so that the diameter-reduced part of the outer brick layer 30 may be filled.

In the immersion tube 1 of the present embodiment, as shown in FIG. 6, the outer diameter of the castable layer 32 matches the outer diameter at the portion of the outer brick layer 30. That is, in the immersion pipe 1 of the present embodiment, the outer peripheral surface of the outer peripheral brick layer 30 and the outer peripheral surface of the castable layer 32 are formed to have the same diameter.
Also in the immersion tube 1 of the present embodiment, the radially outer end of the interface between the end surface 30 a of the lower end of the outer peripheral brick layer 30 and the castable layer 32 is covered with the covering portion 37 of the castable layer 32. It exerts the same effect as

Fourth Embodiment
The present embodiment is the same immersion tube 1 as the third embodiment except that the configuration in the vicinity of the lower end portion of the outer brick layer 30 is different. The configuration in the vicinity of the lower end portion of the outer brick layer 30 of the immersion tube 1 of the present embodiment is shown in FIG. 7 in an enlarged sectional view.

As shown in FIG. 7, the immersion tube 1 of the present embodiment is formed such that the diameter in the vicinity of the lower end portion of the outer peripheral surface of the outer brick layer 30 is reduced. And the covering part 37 of the castable layer 32 is formed so that the diameter-reduced part of the outer brick layer 30 may be filled. Then, the end face of the upper part of the covering portion 37 (and the corresponding surface of the reduced diameter portion of the outer brick layer 30 corresponding to this surface) is formed to be inclined.
Also in the immersion tube 1 of the present embodiment, the radially outer end of the interface between the end surface 30a of the lower end of the outer peripheral brick layer 30 and the castable layer 32 is covered with the covering portion 37 of the castable layer 32. It exerts the same effect as

Hereinafter, the present invention will be specifically described using examples.
The immersion tube 1 of Embodiment 1 was manufactured as an example of the present invention. In addition, the structure of the coating | coated part 37 vicinity of the immersion pipe 1 of each Example and a comparative example was shown by the expanded sectional view in FIG.
Example 1
In the immersion pipe 1 of this example, in FIG. 8, the length (L1) of the covering portion 37 is 30 mm, and the thickness (L2) of the covering portion 37 is 15 mm.
(Example 2)
In the immersion tube 1 of this example, in FIG. 8, the length (L1) of the covering portion 37 is 50 mm, and the thickness (L2) of the covering portion 37 is 15 mm.

(Example 3)
In the immersion pipe 1 of this example, in FIG. 8, the length (L1) of the covering portion 37 is 80 mm, and the thickness (L2) of the covering portion 37 is 15 mm.
(Example 4)
In the immersion tube 1 of this example, in FIG. 8, the length (L1) of the covering portion 37 is 100 mm, and the thickness (L2) of the covering portion 37 is 15 mm.

(Example 5)
In the immersion pipe 1 of this example, in FIG. 8, the length (L1) of the covering portion 37 is 130 mm, and the thickness (L2) of the covering portion 37 is 15 mm.
(Example 6)
In the immersion pipe 1 of this example, in FIG. 8, the length (L1) of the covering portion 37 is 150 mm, and the thickness (L2) of the covering portion 37 is 15 mm.
(Example 7)
In the immersion tube 1 of this example, in FIG. 8, the length (L1) of the covering portion 37 is 200 mm, and the thickness (L2) of the covering portion 37 is 15 mm.

(Comparative example 1)
In the immersion tube 1 of this example, the covering portion 37 is not formed in FIG. That is, the length (L1) of the covering portion 37 is 0 mm, and the thickness (L2) of the covering portion 37 is 0 mm.

(Evaluation)
The immersion pipes 1 of the embodiment and the comparative example were assembled as the rising pipe 1a of the vacuum degassing apparatus 4, and the vacuum degassing apparatus 4 was operated to reflux the molten steel for a predetermined time.

After a predetermined time has elapsed, the immersion pipe 1 is removed from the vacuum degassing apparatus 4 and the immersion pipe 1 is disassembled to determine whether or not the molten metal 43 intrudes into the interface between the end face 30a of the lower end of the outer peripheral brick layer 30 and the castable layer 32. The thickness (boundary base metal thickness) of the steel formed from the invading molten metal 43 and the presence or absence of damage to the metal core body 20 were observed. The observation results are shown in Table 1. In addition, boundary ground metal thickness was taken as the average thickness in a plurality of places in the circumferential direction (specifically, four places located at equal intervals in the circumferential direction).
In the comprehensive evaluation in Table 1, the damage (dissolution) of the metal core body 20 was confirmed, and the one not suitable for the use of the immersion tube 1 is x, and the dissolution was confirmed even if it was confirmed. The amount of loss was slight, and the one that could be used for the immersion tube 1 was Δ, and the one without melting loss was 〇 or more. And, among those without melting damage, those having a boundary metal thickness of 2 mm or less were regarded as ◎.

  As shown in Table 1, in Comparative Example 1 in which the covering portion 37 is not formed, molten steel intrudes into the interface between the end surface 30a of the lower end of the outer peripheral brick layer 30 and the castable layer 32, and steel formed from this molten steel The thickness of the was increased to 10 mm. Furthermore, the molten steel that has intruded into the interface causes the core metal body 20 to be melted away. That is, in Comparative Example 1, it was confirmed that the core metal main body 20 was damaged so that further use of the immersion tube 1 was impossible.

On the other hand, in Examples 1 to 7 in which the covering portion 37 is formed, the boundary metal thickness is smaller than that of Comparative Example 1. By the presence of the covering portion 37, the penetration of the molten metal 43 can be suppressed, and the occurrence of melting damage can be suppressed. Even if melting loss occurs, the amount of melting loss can be suppressed to such an extent that further use of the immersion pipe 1 is possible (that is, continuous use of the immersion pipe 1 is possible).
As the length (L1) of the covering portion 37 is longer, the boundary metal thickness is smaller. And when the length (L1) of the coating | coated part 37 will be 50 mm or more like Examples 2-7, the melting loss of the immersion tube 1 was not confirmed. As in Examples 5 to 7, when the length (L1) of the covering portion 37 is 130 mm or more, no boundary metal is observed (the thickness of the boundary metal is zero), and penetration of the molten metal 43 into the interface is confirmed. It was not.

  As described above, in the immersion pipe 1 of each embodiment, the radially outer end of the interface between the end surface 30 a of the lower end of the outer peripheral brick layer 30 and the castable layer 32 is covered with the covering portion 37 of the castable layer 32. Even when the lower end of the immersion tube 1 is immersed in the molten metal 43, the interface between the end surface 30a of the lower end of the outer peripheral brick layer 30 and the castable layer 32 is not exposed to the molten metal 43. For this reason, the penetration of the molten metal 43 into the interface between the end surface 30a of the lower end of the outer peripheral brick layer 30 and the castable layer 32 is suppressed, and the damage of the immersion pipe 1 due to the penetration of the molten metal 43 is suppressed.

  Further, the outer diameter side end of the interface between the outer peripheral brick layer 30 and the castable layer 32 is located on the outer peripheral surface of the outer peripheral brick layer 30. Then, even if the molten metal 43 intrudes into the end of this boundary, the molten metal 43 infiltrates downward along the outer peripheral surface of the outer peripheral brick layer 30, and the molten metal 43 is in the end face 30a of the lower end of the outer peripheral brick layer 30. It is difficult to reach. As a result, damage to the immersion tube 1 due to the penetration of the molten metal 43 was suppressed.

1: Immersion tube 2: core metal, 20: core metal body, 21 and 22: brick press fitting, 23: stud 3: refractory layer, 30: outer brick layer, 31: inner brick layer, 32: castable layer, 33 , 34: refractory brick, 35, 36: castable layer, 37: coating portion 4: vacuum degassing device, 40: upper tank, 41: lower tank, 42: ladle, 43: molten metal

Claims (4)

With a cylindrical core metal,
An outer peripheral brick layer formed in a tubular shape constituted by a plurality of bricks arranged along the outer peripheral surface of the core metal;
A castable layer disposed on the lower side of at least the core metal;
In the dip tube having
The said castable layer covers the lower end part of the outer peripheral surface of the said outer periphery brick layer, It is formed so that the said outer peripheral surface of the said outer periphery brick layer may be exposed in the upper part .   The immersion tube according to claim 1, wherein the castable layer is a formed body formed by pouring a material having fluidity. The said castable layer covers the lower end part of the outer peripheral surface of the said outer periphery brick layer by 50 mm or more in length, The immersion pipe of any one of Claims 1-2 . The immersion pipe according to any one of claims 1 to 3 , wherein the brick forming the outer peripheral brick layer is made of magnesia carbon.

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