A low thermal conductive dip tube and a method of making

Abstract

The present application provides a low-thermal-conductivity immersion tube and a preparation method thereof, comprising a steel casing, an outer part of the steel casing having a cast layer formed by pouring refractory material, and an inner part of the steel casing having a refractory brick, an outer wall of a lower part of the steel casing for inserting a molten steel being fixed with a heat insulation plate, the heat insulation plate being located in the cast layer; a gap being formed between an inner wall of the steel casing and the refractory brick, a low-thermal-conductivity cast layer being formed by pouring low-thermal-conductivity cast material into the gap, the low-thermal-conductivity cast material having a hollow structure. The present application uses the heat insulation plate and the low-thermal-conductivity cast material to reduce the temperature of the steel casing and reduce the thermal stress between the steel casing and the refractory material, thereby prolonging the service life of the immersion tube.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of RH immersion tube, in particular to a low-thermal-conductivity immersion tube and a preparation method thereof. BACKGROUND

[0002] RH is a vacuum circulation degassing method of liquid steel, which is designed and developed by Ruhrstahl and Hereaeus. RH refining can remove hydrogen, nitrogen, oxygen, carbon, sulfur from molten steel, homogenize the composition of molten steel, and improve the cleanliness of molten steel. Its advantages are: easy operation, good refining effect, short processing time and large production capacity. Therefore, RH refining is an indispensable process for clean steel smelting. The RH immersion tube frequently withstands rapid cooling and rapid heating during the production process. Due to the difference in expansion coefficient between the steel structure and the refractory material, the refractory bricks inside the steel structure are loose and fall off, cracks and air leakage occur in the external castable, which leads to difficulty in controlling the nitrogen content of molten steel, deformation of the steel structure at the gap, and greatly reduces the service life. Therefore, the RH immersion tube obviously affects the metallurgical function of RH.

[0003] CN202122474532.7 discloses an immersion tube with a wind cooling device, which reduces the temperature of the inner container by increasing the wind cooling chamber on the outer surface of the inner container, improves the continuous smelting, and prolongs the service life. CN201920757283.2 discloses a cooling device for RH refining furnace insertion pipe, a cylindrical structure cooling chamber is welded on the outer wall of the insertion pipe, and cold water inlet pipe and hot water outlet pipe are installed on the outer wall of the cooling chamber. The redness and deformation of the metal steel structure of the insertion pipe are relieved, and the service life of the RH vacuum furnace insertion pipe is improved. Disadvantages: complex structure, increased process temperature drop.

[0004] CN201610554088.0 discloses an RH vacuum furnace low-stress immersion tube, which comprises, from inside to outside, a refractory brick lining, a filling layer and a steel cylinder. The steel cylinder wall is not perforated, and the steel cylinder bottom is welded with an annular metal pipe or an annular metal rod. The outer wall below the top of the steel cylinder and the outer wall of the annular metal pipe or the annular metal rod are both paved with a buffer layer. The outer wall of the steel cylinder and the outer wall of the annular metal pipe or the annular metal rod are uniformly welded with V-shaped metal anchor and double V-shaped metal anchor along the axial direction of the steel cylinder, and the V-shaped metal anchor and the double V-shaped metal anchor pass through the buffer layer. The damage and deterioration problem caused by the significant difference in material performance between the components in the immersion tube composite structure is relieved, the stress and thermal stress of the immersion tube structure are reduced, and the service life of the immersion tube is prolonged. Disadvantages: cannot reduce the temperature of the steel cylinder, and the thermal stress still alternates.

[0005] Document "Influence of Steel Tube Grooving on Thermal Expansion of RH Immersion Tube", Refractories, 2015, 49(1): 56-58, in order to solve the cracking and falling of RH immersion tube refractory, the finite element model of the refractory brick-steel tube-pouring material composite structure immersion tube is established by using ANSYS software, the steel tube grooving immersion tube is analyzed and calculated, and the simulation test and actual application test are carried out. The results show that the steel tube grooving is one of the effective methods to reduce the thermal expansion of the steel tube. Disadvantages: reduce the strength of the steel tube.

[0006] In summary, there is no relevant report to disclose the method of reducing the thermal stress between the steel tube and the refractory material during use without affecting the strength of the steel tube and improving the structure of the immersion tube. SUMMARY

[0007] According to the above technical problems, a low thermal conductivity immersion tube is provided.

[0008] The technical means adopted by the present application are as follows:

[0009] A low thermal conductivity immersion tube, comprising a steel tube, the outer part of the steel tube has a pouring layer formed by pouring refractory material, and the inner part has a refractory brick, the outer wall of the lower part of the steel tube for inserting the molten steel is fixed with a heat insulation plate, and the heat insulation plate is located in the pouring layer; there is a gap between the inner wall of the steel tube and the refractory brick, and a low thermal conductivity pouring layer is formed by pouring low thermal conductivity pouring material in the gap, and the low thermal conductivity pouring material has a hollow structure.

[0010] Preferably, the pouring layer has a plurality of anchor pieces fixed to the outer wall of the steel tube.

[0011] Preferably, the refractory material pouring material is alumina pouring material, which comprises: 10-15 parts of alumina with particle size of 3-5 mm, 15-25 parts of alumina with particle size of 1-3 mm, 20-30 parts of alumina with particle size of 0-1 mm, 25-35 parts of alumina with particle size of <0.074 mm, 2-4 parts of silica powder, 3-6 parts of active alumina 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 part of explosion-proof fiber, and 6-7 parts of water.

[0012] Preferably, the low-thermal-conductivity casting material comprises: 10-15 parts of alumina with a particle size of 3-5 mm, 15-20 parts of alumina hollow 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 of <0.074 mm, 2-4 parts of silica powder, 3-6 parts of active alumina powder, 1-2 parts of high-alumina cement, 0.5-1 part of water-reducing agent, 0.4 parts of anti-explosion fiber, and 6-7 parts of water. That is, the alumina hollow spheres are added in the alumina casting material, and the slow heat conduction rate of the hollow spheres is used to reduce the heat transfer of the refractory brick to the steel tube.

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

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

[0015] Preferably, the refractory brick is a chrome-free brick.

[0016] The application also discloses a preparation method of the low-thermal-conductivity immersed tube.

[0017] The distance for inserting the steel tube into the molten steel is determined, and the heat insulation plate is fixed to the outer wall of the part of the lower part of the steel tube for inserting the molten steel;

[0018] The refractory brick is built in the steel tube, and the gap is formed between the inner wall of the steel tube and the chrome-free brick;

[0019] The whole is put into a mold, and the refractory material casting material is injected from the outside;

[0020] The low-thermal-conductivity casting material is cast in the gap;

[0021] The low-thermal-conductivity immersed tube is formed through vibration forming, curing, demolding and baking.

[0022] Compared with the prior art, the application has the following advantages:

[0023] In the traditional process, the alumina casting layer is directly arranged on the outer wall of the steel tube, and the chrome-free brick is directly arranged on the inner wall of the steel tube. During the use of the immersed tube, the immersed tube bears the rapid cooling or rapid heating change of temperature, and the thermal expansion coefficient of the steel tube is different from the thermal expansion coefficients of the alumina casting layer and the chrome-free brick, so that cracks are generated in the refractory material, gas leakage is prone to occur, and the control of the nitrogen content of the molten steel is difficult. The steel structure at the gap is deformed, and the service life is greatly reduced. In the application, the heat insulation plate is arranged on the outer wall of the steel tube, and the low-thermal-conductivity casting material is arranged on the inner wall of the steel tube, so that the heat received by the steel tube from the outside and the inside is reduced, the temperature change of the steel tube is small, the thermal stress between the steel tube and the refractory material is reduced, and the service life of the immersed tube is improved.

[0024] Based on the above reasons, the present application can be widely popularized in the field of RH immersion tube, etc. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings described below are only some embodiments of the present application, and the other drawings can also be obtained by those skilled in the art without creative labor.

[0026] Figure 1 It is a structure diagram of a low-thermal-conductivity immersion tube in the specific embodiment of the present application.

[0027] In the figure: 1, steel tube; 2, molten steel; 3, heat insulation plate; 4, chrome-free brick; 5, low-thermal-conductivity pouring layer; 6, alumina pouring layer; 7, anchor. DETAILED DESCRIPTION

[0028] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the drawings and in combination with the embodiments.

[0029] In order to make the purpose, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the drawings of the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all. The description of the at least one exemplary embodiment is actually only illustrative, but not as any limitation on the present application and its application or use. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0030] It should be noted that the terms used herein are only for describing the specific embodiments, and are not intended to limit the exemplary embodiments according to the present application. As used herein, the singular form is intended to include the plural form unless the context clearly indicates otherwise, and it should also be understood that when the terms "comprise" and / or "include" are used in the specification, there is a feature, step, operation, device, component and / or combination thereof.

[0031] The foregoing is considered as illustrative only of the principles of the application. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the application to the exact construction and practice described. Accordingly, all such variations are intended to be included within the scope of the present application as defined in the following claims, along with full equivalents thereof.

[0032] In the description of the present application, it is to be understood that the orientation terms such as "front", "back", "up", "down", "left", "right", "transverse", "vertical", "horizontal", "top", "bottom", etc. indicate the orientation or positional relationship shown in the drawings, which are merely for the convenience of describing and simplifying the present application, and do not indicate or imply that the devices or elements referred to must have a particular orientation or be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the scope of protection of the present application. The orientation terms "inner", "outer" refer to the inner and outer relative to the contour of the components themselves.

[0033] For the convenience of description, spatial relative terms such as "over", "above", "upper surface", "upper", etc. can be used herein to describe the spatial positional relationship of one device or feature with respect to other devices or features as shown in the drawings. It should be understood that the spatial relative terms are intended to include different orientations in use or operation in addition to the orientation of the devices described in the drawings. For example, if the devices in the drawings are inverted, the device described as "above" or "over" other devices or structures will be positioned "below" or "under" the other devices or structures. Thus, the exemplary term "above" can include both "above" and "below" orientations. The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein are interpreted accordingly.

[0034] In addition, it should be noted that the use of the terms "first", "second", etc. to qualify parts of components is merely for the convenience of distinguishing the corresponding parts of components, and the above terms have no special meaning unless otherwise stated, and therefore cannot be understood as a limitation on the scope of protection of the present application.

[0035] As Figure 1As shown, a low-thermal-conductivity immersion tube comprises a steel casing 1, the outer wall of the lower part of which for inserting into the liquid steel 2 is fixed with a 10-30mm-thick heat-insulating plate 3, the heat-insulating plate 3 being a high-alumina heat-insulating plate with a thermal conductivity of 0.035-0.09W / (m·K); the steel casing 1 is lined with chromium-free bricks 4, and the inner wall of the steel casing 1 and the chromium-free bricks 4 have a gap of 30-50mm; the gap is poured with low-thermal-conductivity casting material to form a low-thermal-conductivity casting layer 5, the low-thermal-conductivity casting material having a hollow structure; and the outer wall of the steel casing 1 is poured with alumina casting material to form an alumina casting layer 6.

[0036] The alumina casting layer 6 has a plurality of anchor pieces 7 fixed to the outer wall of the steel casing 1, the anchor pieces 7 being welded to the outer wall of the steel casing 1 during installation, then the heat-insulating plate 3 is installed, a limiting device (such as a limiting pin or the like) is arranged on the anchor pieces 7 to prevent the heat-insulating plate 3 from moving, and then pouring is performed.

[0037] The alumina casting material 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 of <0.074mm, 2-4 parts of silicon powder, 3-6 parts of active alumina 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 part of explosion-proof fiber, and 6-7 parts of water.

[0038] The low-thermal-conductivity casting material comprises 10-15 parts of alumina with a particle size of 3-5mm, 15-20 parts of alumina hollow spheres with an outer diameter of 2-5mm, 15-20 parts of alumina with a particle size of 1-3mm, 20-25 parts of alumina with a particle size of 0-1mm, 25-35 parts of alumina with a particle size of <0.074mm, 2-4 parts of silicon powder, 3-6 parts of active alumina powder, 1-2 parts of high-alumina cement, 0.5-1 part of water-reducing agent, 0.4 part of explosion-proof fiber, and 6-7 parts of water.

[0039] The application further discloses a preparation method of the low-thermal-conductivity immersion tube.

[0040] The distance for inserting the steel casing 1 into the liquid steel 2 is determined, and the heat-insulating plate 3 is fixed to the outer wall of the lower part of the steel casing 1 for inserting into the liquid steel 2;

[0041] The chromium-free bricks 4 are lined in the steel casing 1, and the inner wall of the steel casing 1 and the chromium-free bricks 4 have the gap;

[0042] The whole is put into a mold, and the outer side is poured with alumina casting material;

[0043] The low-thermal-conductivity casting material is poured into the gap;

[0044] Vibration forming, curing, demolding, baking to form low thermal conductivity impregnation tube.

[0045] Example 1

[0046] Determine the distance of the steel casing 1 for inserting the molten steel 2 depth, and the outer wall of the part of the steel casing 1 for inserting the molten steel 2 is fixed with 10mm thick insulation board 3, the inside of the steel casing 1 is lined with chrome-free brick 4, and the gap between the steel casing 1 and the chrome-free brick 4 is 30mm. The whole is put into the mold, and the outside is injected with alumina casting material. The composition of the alumina casting material is: 10 parts of alumina with particle size of 5~3mm, 25 parts of alumina with particle size of 3~1mm, 20 parts of alumina with particle size of 1~0mm, 35 parts of alumina with particle size <0.074mm, 2 parts of silicon powder, 5 parts of active alumina powder, 1.5 parts of high alumina cement, 1 part of stainless steel fiber, 0.5 part of water reducing agent, 0.4 part of explosion-proof fiber, and 6~7 parts of water. The gap between the steel casing 1 and the chrome-free brick 4 is injected with low thermal conductivity casting material. The composition of the low thermal conductivity casting material is: 10 parts of alumina with particle size of 5~3mm, 15 parts of alumina hollow sphere with outer diameter of 2~5mm, 15 parts of alumina with particle size of 3~1mm, 20 parts of alumina with particle size of 1~0mm, 30 parts of alumina with particle size <0.074mm, 3 parts of silicon powder, 5 parts of active alumina powder, 1.5 parts of high alumina cement, 0.5 parts of water reducing agent, 0.4 parts of explosion-proof fiber, and 6~7 parts of water. Vibration forming, curing for 24h, demolding, and baking to obtain low thermal conductivity impregnation tube. Compared with the existing impregnation tube, the service life is increased by 10 furnaces.

[0047] Example 2

[0048] Determine the distance of the steel casing 1 for inserting the molten steel 2 depth, and the lower part of the steel casing 1 for inserting the molten steel 2 part of the outer wall fixed 20mm thick insulation board 3, steel casing 1 inside the brick 4 without chrome, steel casing 1 and the gap between the chrome-free brick 4 40mm. Put into the mold as a whole outside injection of alumina castable, the composition of the alumina castable: particle size 5~3mm of alumina 10 parts, particle size 3~1mm of alumina 20 parts, particle size 1~0mm of alumina 25 parts, particle size <0.074mm of alumina 35 parts, silicon powder 2 parts, active alumina powder 5 parts, high alumina cement 1.5 parts, stainless steel fiber 1.5 parts, water reducing agent 0.5 parts, explosion-proof fiber 0.4 parts, water 6~7 parts. Steel casing 1 and the gap between the chrome-free brick 4 injection low thermal conductivity castable, the composition of the low thermal conductivity castable: particle size 5~3mm of alumina 13 parts, outer diameter 2~5mm of alumina hollow sphere 17 parts, particle size 3~1mm of alumina 10 parts, particle size 1~0mm of alumina 20 parts, particle size <0.074mm of alumina 30 parts, silicon powder 4 parts, active alumina powder 4 parts, high alumina cement 1.5 parts, water reducing agent 0.5 parts, explosion-proof fiber 0.4 parts, water 6~7 parts. Vibration forming, demoulding after 24h curing, and then get low thermal conductivity impregnated tube after baking, compared with the existing impregnated tube, service life increased by 13 furnace.

[0049] Example 3

[0050] Determine the distance of the steel casing 1 for inserting the molten steel 2 depth, and the lower part of the steel casing 1 for inserting the molten steel 2 part of the outer wall fixed 20mm thick insulation board 3, steel casing 1 inside the brick 4 without chrome, steel casing 1 and the gap between the chrome-free brick 4 40mm. Put into the mold as a whole outside injection of alumina castable, the composition of the alumina castable: particle size 5~3mm of alumina 10 parts, particle size 3~1mm of alumina 20 parts, particle size 1~0mm of alumina 25 parts, particle size <0.074mm of alumina 35 parts, silicon powder 2 parts, active alumina powder 5 parts, high alumina cement 1.5 parts, stainless steel fiber 1.5 parts, water reducing agent 0.5 parts, explosion-proof fiber 0.4 parts, water 6~7 parts. Steel casing 1 and the gap between the chrome-free brick 4 injection low thermal conductivity castable, the composition of the low thermal conductivity castable: particle size 5~3mm of alumina 13 parts, outer diameter 2~5mm of alumina hollow sphere 17 parts, particle size 3~1mm of alumina 10 parts, particle size 1~0mm of alumina 20 parts, particle size <0.074mm of alumina 30 parts, silicon powder 4 parts, active alumina powder 4 parts, high alumina cement 1.5 parts, water reducing agent 0.5 parts, explosion-proof fiber 0.4 parts, water 6~7 parts. Vibration forming, demoulding after 24h curing, and then get low thermal conductivity impregnated tube after baking, compared with the existing impregnated tube, service life increased by 13 furnace.

[0051] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit the present application; although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions recorded in the above embodiments can be modified, or some or all of the technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A low thermal conductivity impregnated pipe, comprising a steel liner, wherein the outer surface of the steel liner has a casting layer formed by casting refractory castable, and the inner surface has refractory bricks, characterized in that, An insulation plate is fixed to the outer wall of the lower part of the steel liner for inserting molten steel, and the insulation plate is located within the casting layer; there is a gap of 30-50mm between the inner wall of the steel liner and the refractory bricks; the insulation plate is 10-30mm thick, is a high-alumina insulation plate, and has a thermal conductivity of 0.035-0.09W / (m·K); a low thermal conductivity castable is poured into the gap to form a low thermal conductivity casting layer, and the low thermal conductivity castable has a hollow structure. 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; The refractory bricks are chrome-free bricks.

2. The low thermal conductivity impregnated 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 thermal conductivity impregnated 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. A method for preparing a low thermal conductivity impregnated tube according to any one of claims 1 to 3, characterized in that, include: Determine the distance at which the steel tank is used to insert into the molten steel, and fix the insulation plate to the outer wall of the lower part of the steel tank used for inserting into the molten steel; The steel liner is lined with the refractory bricks, and there is a gap between the inner wall of the steel liner and the chromium-free bricks; The entire assembly is placed into the mold, and the refractory castable is injected into the outer side. The low thermal conductivity castable is poured into the gap; Vibration molding, curing, demolding, and baking are used to form low thermal conductivity impregnated tubes.

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