A low-expansion impregnated tube and method of making

Abstract

The application provides a low-expansion immersion tube and a preparation method thereof, which comprises a steel casing, aluminum sheets fixed on the inner wall and the outer wall of the steel casing respectively, a pouring layer on the outer wall of the steel casing, an insulating plate fixed on the aluminum sheet corresponding to the outer wall of the lower part of the steel casing for inserting the molten steel, and a refractory brick in the steel casing; a gap is formed between the aluminum sheet on the inner side and the refractory brick, a low-thermal-conductivity pouring material is poured into the gap to form a low-thermal-conductivity pouring layer, and the low-thermal-conductivity pouring material has a hollow structure. The application reduces the temperature of the steel casing by using the insulating plate and the low-thermal-conductivity pouring material, reduces the thermal stress between the steel casing and the refractory material, and further reduces the thermal stress between the steel casing and the refractory material during use by using the aluminum sheet which is easy to deform, thereby prolonging the service life of the immersion tube.

Description

Technical Field

[0001] This invention relates to the field of RH impregnation tube technology, and more specifically to a low-expansion impregnation tube and its preparation method. Background Technology

[0002] RH, or molten steel vacuum circulation degassing, is a ladle refining method for molten steel jointly designed and developed by Ruhrstahl and Hereaeus. RH refining can dehydrogenate, denitrify, deoxidize, decarburize, desulfurize, homogenize the composition of molten steel, and improve its cleanliness. Its advantages include convenient operation, good refining effect, short processing time, and high production capacity. Therefore, RH refining is an indispensable process in clean steel smelting. RH-impregnated tubes are frequently subjected to rapid heating and cooling during production. Due to the difference in expansion coefficients between the steel structure and the refractory material, the refractory bricks inside the steel structure become loose and fall off, and cracks and air leaks occur in the external castable, making it difficult to control the nitrogen content of the molten steel. Deformation of the steel structure at the gaps significantly reduces its service life. Therefore, RH-impregnated tubes significantly affect the metallurgical properties of RH.

[0003] CN202122474532.7 discloses an impregnation tube with an air-cooling device. By adding an air-cooling chamber to the outer surface of the inner liner, the temperature of the inner liner is reduced, improving continuous smelting performance and extending service life. CN201920757283.2 discloses a cooling device for an insert tube in an RH refining furnace. A cylindrical cooling chamber is welded to the upper part of the outer wall of the insert tube. A cold water inlet pipe and a hot water outlet pipe are installed on the outer wall of the cooling chamber, alleviating the red-hot and deformation of the metal steel structure of the insert tube and improving the service life of the insert tube in an RH vacuum furnace. Disadvantages: The structure is relatively complex, increasing process temperature drop.

[0004] CN201610554088.0 discloses a low-stress impregnation tube for an RH vacuum furnace, comprising, from the inside out, a refractory brick lining, a filling layer, and a steel cylinder. The steel cylinder wall is not perforated, and an annular metal tube or annular metal rod is welded to the bottom surface of the steel cylinder. Buffer layers are laid on the outer wall below the top of the steel cylinder and on the outer wall of the annular metal tube or annular metal rod. V-shaped metal anchors and double V-shaped metal anchors are uniformly welded circumferentially in layers along the axial direction of the steel cylinder and the outer wall of the annular metal tube or annular metal rod, with the V-shaped and double V-shaped metal anchors passing through the buffer layer. This design alleviates the damage and deterioration problem caused by significant differences in material properties between components in the impregnation tube composite structure, thereby reducing structural and thermal stress and extending the service life of the impregnation tube. Disadvantage: It cannot reduce the temperature of the steel cylinder, and thermal stress still occurs alternately.

[0005] The literature "Influence of Steel Tank Grooving Method on Thermal Expansion of RH Impregnated Tubes, Refractory Materials, 2015, 49(1):56~58" describes a finite element model of a composite structure impregnated tube made of refractory brick, steel tank, and castable refractory. The model was used to analyze and calculate the grooved steel tank, and simulation and practical application tests were conducted. The results show that grooving the steel tank is an effective way to reduce its thermal expansion. However, it also reduces the strength of the steel tank.

[0006] In summary, there are no publicly available reports on methods or techniques for improving the structure of impregnated tubes by reducing thermal stress between the steel liner and refractory materials during use without affecting the strength of the steel liner. Summary of the Invention

[0007] To address the aforementioned technical problems, a low-expansion impregnation tube and its preparation method are provided.

[0008] The technical means employed in this invention are as follows:

[0009] A low-expansion impregnation tube includes a steel liner. The steel liner has an outer casting layer formed by casting refractory castable and an inner refractory brick. Aluminum sheets are fixed to the inner and outer surfaces of the steel liner. An insulation plate is fixed to the aluminum sheet corresponding to the outer wall of the lower part of the steel liner for inserting molten steel. The insulation plate is located within the casting layer. There is a gap between the inner aluminum sheet and the refractory brick. A low-thermal-conductivity castable is poured into the gap to form a low-thermal-conductivity castable layer. The low-thermal-conductivity castable has a hollow structure. The upper and lower ends of the inner aluminum sheet are sealed within the low-thermal-conductivity castable layer, and the upper and lower ends of the outer aluminum sheet are sealed within the castable layer.

[0010] Preferably, the casting layer has a plurality of anchors fixed to the outer wall of the steel liner.

[0011] Preferably, the refractory castable is an alumina castable, comprising: 10-15 parts of alumina with a particle size of 3-5mm, 15-25 parts of alumina with a particle size of 1-3mm, 20-30 parts of alumina with a particle size of 0-1mm, 25-35 parts of alumina with a particle size <0.074mm, 2-4 parts of silica powder, 3-6 parts of activated alumina fine powder, 1-2 parts of high-alumina cement, 1-1.5 parts of stainless steel fiber, 0.5-1 part of water-reducing agent, 0.4 parts of explosion-proof fiber, and 6-7 parts of water.

[0012] Preferably, the low thermal conductivity castable comprises: 10-15 parts of alumina with a particle size of 3-5 mm, 15-20 parts of hollow alumina spheres with an outer diameter of 2-5 mm, 15-20 parts of alumina with a particle size of 1-3 mm, 20-25 parts of alumina with a particle size of 0-1 mm, 25-35 parts of alumina with a particle size <0.074 mm, 2-4 parts of silica powder, 3-6 parts of activated alumina fine powder, 1-2 parts of high-alumina cement, 0.5-1 part of water-reducing agent, 0.4 parts of explosion-proof fiber, and 6-7 parts of water.

[0013] Preferably, the gap is 30~50mm.

[0014] Preferably, the insulation board has a thickness of 10~30mm, is a high-alumina insulation board, and has a thermal conductivity of 0.035-0.09W / (m·K).

[0015] Preferably, the thickness of the aluminum sheet is 2.0~4.0mm.

[0016] Preferably, the refractory brick is a chrome-free brick.

[0017] This invention also discloses a method for preparing a low-expansion impregnation tube, comprising:

[0018] The aluminum sheets are fixed to the inner and outer walls of the steel liner, respectively.

[0019] Determine the distance at which the steel tank is used to insert into the molten steel, and fix the insulation plate on the aluminum sheet corresponding to the outer wall of the lower part of the steel tank used to insert into the molten steel;

[0020] The steel liner is lined with refractory bricks, and there is a gap between the aluminum sheet on the inner side and the chromium-free bricks.

[0021] The entire assembly is placed into the mold, and the refractory casting material is injected into the outside. The upper and lower ends of the aluminum sheet located on the outside are sealed in the refractory casting material.

[0022] The low thermal conductivity castable is poured into the gap, and the upper and lower ends of the aluminum sheet located on the inner side are sealed in the low thermal conductivity castable.

[0023] Vibration molding, curing, demolding, and baking are used to form low-expansion impregnated tubes.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] In traditional processes, an alumina casting layer is directly applied to the outer wall of the steel liner, while chromium-free bricks are directly applied to the inner wall. During use, the impregnating tube is subjected to rapid temperature changes, and the thermal expansion coefficients of the steel liner, alumina casting layer, and chromium-free bricks differ, leading to cracks in the refractory material, easy gas leakage, and difficulty in controlling the nitrogen content of the molten steel. Deformation of the steel structure at the gaps significantly reduces its service life. This invention addresses this by applying an insulation board and aluminum sheets to the outer wall of the steel liner and a low-thermal-conductivity castable to the inner wall. This reduces the amount of heat received by the steel liner from both the outside and inside, resulting in smaller temperature variations and reduced thermal stress between the steel liner and the refractory material. Furthermore, the easily deformable aluminum sheets further reduce thermal stress between the steel liner and the refractory material during use, thus improving the service life of the impregnating tube.

[0026] Based on the above reasons, this invention can be widely applied in fields such as RH impregnation tubes. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a schematic diagram of an RH-impregnated tube structure according to a specific embodiment of the present invention.

[0029] In the diagram: 1. Steel liner; 2. Molten steel; 3. Insulation board; 4. Chromium-free brick; 5. Low thermal conductivity casting layer; 6. Alumina casting layer; 7. Anchor; 8. Aluminum sheet. Detailed Implementation

[0030] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0033] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0034] In the description of this invention, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is generally based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this invention and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this invention. The directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0035] For ease of description, spatial relative terms such as "above," "over," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation besides the orientation of the device as described in the figures. For example, if the device in the figures is inverted, a device described as "above" or "above" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0036] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0037] like Figure 1 As shown, a low-expansion impregnation tube includes a steel liner 1, with aluminum sheets 8 fixed to its inner and outer surfaces respectively.

[0038] A 10-30mm thick insulation board 3 is fixed to the aluminum sheet 8 corresponding to the lower part of the steel tank 1 where the molten steel 2 is inserted. The insulation board 3 is a high-alumina insulation board with a thermal conductivity of 0.035-0.09 W / (m·K). The steel tank 1 is lined with chrome-free bricks 4, and there is a 30-50mm gap between the inner aluminum sheet 8 and the chrome-free bricks 4. A low-thermal-conductivity castable is poured into the gap to form a low-thermal-conductivity castable layer 5. The upper and lower ends of the inner aluminum sheet 8 are sealed within the low-thermal-conductivity castable layer 5, which has a hollow structure. An alumina castable is poured onto the outside of the steel tank 1 to form an alumina castable layer 6. The upper and lower ends of the outer aluminum sheet 8 are sealed within the alumina castable layer 6.

[0039] The alumina casting layer 6 has multiple anchors 7 fixed to the outer wall of the steel liner 1. During installation, the anchors 7 are first welded to the outer wall of the steel liner 1, and then the outer aluminum sheet 8 and the insulation plate 3 are installed. A limiting device (such as a limiting pin) is set on the anchor 7 to prevent the outer aluminum sheet 8 and the insulation plate 3 from moving. Then the casting is carried out.

[0040] The alumina castable comprises: 10-15 parts of alumina with a particle size of 3-5mm, 15-25 parts of alumina with a particle size of 1-3mm, 20-30 parts of alumina with a particle size of 0-1mm, 25-35 parts of alumina with a particle size <0.074mm, 2-4 parts of silica powder, 3-6 parts of activated alumina fine powder, 1-2 parts of high-alumina cement, 1-1.5 parts of stainless steel fiber, 0.5-1 part of water-reducing agent, 0.4 parts of explosion-proof fiber, and 6-7 parts of water.

[0041] The low thermal conductivity castable comprises: 10-15 parts of alumina with a particle size of 3-5 mm, 15-20 parts of hollow alumina spheres with an outer diameter of 2-5 mm, 15-20 parts of alumina with a particle size of 1-3 mm, 20-25 parts of alumina with a particle size of 0-1 mm, 25-35 parts of alumina with a particle size <0.074 mm, 2-4 parts of silica powder, 3-6 parts of activated alumina fine powder, 1-2 parts of high-alumina cement, 0.5-1 part of water-reducing agent, 0.4 parts of explosion-proof fiber, and 6-7 parts of water.

[0042] This invention also discloses a method for preparing an RH-impregnated tube, comprising:

[0043] The aluminum sheet 8 is fixed to the inner and outer walls of the steel liner 1, respectively;

[0044] Determine the distance at which the steel tank 1 is used to insert the molten steel 2, and fix the heat insulation plate 3 on the aluminum sheet 8 corresponding to the outer wall of the lower part of the steel tank 1 used to insert the molten steel 2;

[0045] The steel liner 1 is lined with the chromium-free brick 4, and the gap is located between the inner aluminum sheet 8 and the chromium-free brick 4;

[0046] The entire piece is placed into the mold, and alumina casting material is injected into the outside; and the upper and lower ends of the aluminum sheet 8 located on the outside are sealed in the alumina casting material;

[0047] The low thermal conductivity castable is poured into the gap, and the upper and lower ends of the aluminum sheet 8 located on the inner side are sealed in the low thermal conductivity castable.

[0048] Vibration molding, curing, demolding, and baking are used to form low-expansion impregnated tubes.

[0049] Example 1

[0050] Aluminum sheets 8, 2.0 mm thick, are fixed to the inner and outer walls of the steel tank 1. The depth at which the steel tank 1 is inserted into the molten steel 2 is determined, and a heat insulation plate 3, 10 mm thick, is fixed to the aluminum sheet 8 corresponding to the lower part of the steel tank 1 used for inserting the molten steel 2. The steel tank 1 is lined with chrome-free bricks 4, and the gap between the aluminum sheet 8 and the chrome-free bricks 4 on the inner side is 30 mm. The entire assembly is placed in a mold, and alumina castable is injected into the outer side. The composition of the alumina castable is as follows: 10 parts of alumina with a particle size of 5-3 mm, 25 parts of alumina with a particle size of 3-1 mm, 20 parts of alumina with a particle size of 1-0 mm, 35 parts of alumina with a particle size <0.074 mm, 2 parts of silica powder, 5 parts of activated alumina fine powder, 1.5 parts of high-alumina cement, 1 part of stainless steel fiber, 0.5 parts of water-reducing agent, 0.4 parts of explosion-proof fiber, and 6-7 parts of water. The upper and lower ends of the aluminum sheet 8 located on the outer side are sealed within the alumina castable. Low thermal conductivity castable is injected into the gap between the aluminum sheet 8 on the inner side and the chromium-free brick 4, and the upper and lower ends of the aluminum sheet 8 located on the inner side are sealed within the low thermal conductivity castable. The low thermal conductivity castable is composed of: 10 parts alumina with a particle size of 5-3mm, 15 parts hollow alumina spheres with an outer diameter of 2-5mm, 15 parts alumina with a particle size of 3-1mm, 20 parts alumina with a particle size of 1-0mm, 30 parts alumina with a particle size <0.074mm, 3 parts silica powder, 5 parts activated alumina fine powder, 1.5 parts high-alumina cement, 0.5 parts water-reducing agent, 0.4 parts explosion-proof fiber, and 6-7 parts water. After vibration molding and curing for 24 hours, the tube is demolded and baked to obtain a low thermal conductivity impregnated tube. Compared with existing impregnated tubes, its service life is increased by 13 heats.

[0051] Example 2

[0052] Aluminum sheets 8, 3.0 mm thick, are fixed to the inner and outer walls of the steel tank 1. The depth at which the steel tank 1 is inserted into the molten steel 2 is determined, and a 20 mm thick insulation board 3 is fixed to the aluminum sheet 8 corresponding to the lower part of the steel tank 1 used for inserting the molten steel 2. The steel tank 1 is lined with chrome-free bricks 4, and the gap between the aluminum sheet 8 and the chrome-free bricks 4 on the inner side is 40 mm. The entire assembly is placed in a mold, and alumina castable is injected into the outer side. The composition of the alumina castable is as follows: 10 parts of alumina with a particle size of 5-3 mm, 20 parts of alumina with a particle size of 3-1 mm, 25 parts of alumina with a particle size of 1-0 mm, 35 parts of alumina with a particle size <0.074 mm, 2 parts of silica powder, 5 parts of activated alumina fine powder, 1.5 parts of high-alumina cement, 1 part of stainless steel fiber, 0.5 parts of water-reducing agent, 0.4 parts of explosion-proof fiber, and 6-7 parts of water. The upper and lower ends of the aluminum sheet 8 located on the outer side are sealed within the alumina castable. Low thermal conductivity castable is injected into the gap between the aluminum sheet 8 on the inner side and the chromium-free brick 4, and the upper and lower ends of the aluminum sheet 8 located on the inner side are sealed within the low thermal conductivity castable. The low thermal conductivity castable is composed of: 13 parts alumina with a particle size of 5-3mm, 17 parts hollow alumina spheres with an outer diameter of 2-5mm, 10 parts alumina with a particle size of 3-1mm, 20 parts alumina with a particle size of 1-0mm, 30 parts alumina with a particle size <0.074mm, 4 parts silica powder, 4 parts activated alumina fine powder, 1.5 parts high-alumina cement, 0.5 parts water-reducing agent, 0.4 parts explosion-proof fiber, and 6-7 parts water. After vibration molding and curing for 24 hours, the tube is demolded and baked to obtain a low thermal conductivity impregnated tube. Compared with existing impregnated tubes, its service life is increased by 16 heats.

[0053] Example 3

[0054] Aluminum sheets 8, each 4.0 mm thick, are fixed to the inner and outer walls of the steel tank 1. The depth at which the steel tank 1 is inserted into the molten steel 2 is determined, and a heat insulation plate 3, 30 mm thick, is fixed to the aluminum sheet 8 corresponding to the lower part of the steel tank 1 used for inserting the molten steel 2. The steel tank 1 is lined with chrome-free bricks 4, and the gap between the aluminum sheet 8 and the chrome-free bricks 4 on the inner side is 50 mm. The entire assembly is placed in a mold, and alumina castable is injected into the outer side. The alumina castable consists of: 10 parts alumina with a particle size of 5-3 mm, 25 parts alumina with a particle size of 3-1 mm, 25 parts alumina with a particle size of 1-0 mm, 30 parts alumina with a particle size <0.074 mm, 4 parts silica powder, 3 parts activated alumina fine powder, 1.5 parts high-alumina cement, 1.5 parts stainless steel fiber, 0.5 parts water-reducing agent, 0.4 parts explosion-proof fiber, and 6-7 parts water. The upper and lower ends of the aluminum sheet 8 located on the outer side are sealed within the alumina castable. Low thermal conductivity castable is injected into the gap between the aluminum sheet 8 located on the inner side and the chromium-free brick 4, and the upper and lower ends of the aluminum sheet 8 located on the inner side are sealed within the low thermal conductivity castable. The composition of the low thermal conductivity castable is: 10 parts alumina with a particle size of 5-3mm, 20 parts hollow alumina spheres with an outer diameter of 2-5mm, 10 parts alumina with a particle size of 3-1mm, 20 parts alumina with a particle size of 1-0mm, 30 parts alumina with a particle size <0.074mm, 2 parts silica powder, 6 parts activated alumina fine powder, 1.5 parts high-alumina cement, 0.5 parts water-reducing agent, 0.4 parts explosion-proof fiber, and 6-7 parts water. Vibration molding is performed, followed by demolding after 24 hours of curing. After baking, the low thermal conductivity impregnated tube is obtained, which has a service life increased by 20 heats compared to existing impregnated tubes.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A low-expansion impregnation pipe, comprising a steel liner, the outer surface of which has a castable layer formed by casting refractory castable, and the inner surface having refractory bricks, characterized in that, Aluminum sheets are fixed to the inner and outer surfaces of the steel liner respectively; an insulation plate is fixed to the aluminum sheet corresponding to the outer wall of the lower part of the steel liner for inserting molten steel, and the insulation plate is located inside the casting layer; there is a gap between the inner aluminum sheet and the refractory brick, and a low thermal conductivity castable is poured into the gap to form a low thermal conductivity casting layer. The low thermal conductivity castable has a hollow structure. The upper and lower ends of the inner aluminum sheet are sealed inside the low thermal conductivity casting layer, and the upper and lower ends of the outer aluminum sheet are sealed inside the casting layer; the refractory brick is a chrome-free brick.

2. The low-expansion impregnation tube according to claim 1, characterized in that, The casting layer has multiple anchors that are fixed to the outer wall of the steel liner.

3. The low-expansion impregnation tube according to claim 1, characterized in that, The refractory castable is an alumina castable, comprising: 10-15 parts of alumina with a particle size of 3-5mm, 15-25 parts of alumina with a particle size of 1-3mm, 20-30 parts of alumina with a particle size of 0-1mm, 25-35 parts of alumina with a particle size <0.074mm, 2-4 parts of silica powder, 3-6 parts of activated alumina fine powder, 1-2 parts of high-alumina cement, 1-1.5 parts of stainless steel fiber, 0.5-1 part of water-reducing agent, 0.4 parts of explosion-proof fiber, and 6-7 parts of water.

4. The low-expansion impregnation tube according to claim 1, characterized in that, The low thermal conductivity castable comprises: 10-15 parts of alumina with a particle size of 3-5 mm, 15-20 parts of hollow alumina spheres with an outer diameter of 2-5 mm, 15-20 parts of alumina with a particle size of 1-3 mm, 20-25 parts of alumina with a particle size of 0-1 mm, 25-35 parts of alumina with a particle size <0.074 mm, 2-4 parts of silica powder, 3-6 parts of activated alumina fine powder, 1-2 parts of high-alumina cement, 0.5-1 part of water-reducing agent, 0.4 parts of explosion-proof fiber, and 6-7 parts of water.

5. A low-expansion impregnation tube according to claim 1, characterized in that, The gap is 30~50mm.

6. The low-expansion impregnation tube according to claim 1, characterized in that, The insulation board has a thickness of 10~30mm and is a high-alumina insulation board with a thermal conductivity of 0.035-0.09W / (m·K).

7. A low-expansion impregnation tube according to claim 1, characterized in that, The thickness of the aluminum sheet is 2.0~4.0mm.

8. A method for preparing a low-expansion impregnation tube according to any one of claims 1 to 7, characterized in that, include: The aluminum sheets are fixed to the inner and outer walls of the steel liner, respectively. Determine the distance at which the steel tank is used to insert into the molten steel, and fix the insulation plate on the aluminum sheet corresponding to the outer wall of the lower part of the steel tank used to insert into the molten steel; The steel liner is lined with refractory bricks, and there is a gap between the aluminum sheet on the inner side and the chromium-free bricks. The entire assembly is placed into the mold, and the refractory casting material is injected into the outside. The upper and lower ends of the aluminum sheet located on the outside are sealed in the refractory casting material. The low thermal conductivity castable is poured into the gap, and the upper and lower ends of the aluminum sheet located on the inner side are sealed in the low thermal conductivity castable. Vibration molding, curing, demolding, and baking are used to form low-expansion impregnated tubes.

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