Ceramic heat-insulating tube and method for manufacturing the same

Abstract

The present application relates to a kind of ceramic heat-insulating pipe and its preparation method, the ceramic heat-insulating pipe includes pipe body, pipe body has central passage, central passage is used to transport fluid;Pipe body is provided with through hole and overheating hole, through hole has multiple and is spaced along the first circumferential direction, metal rod is fixed in through hole, metal rod can be heated by induction;Overheating hole has multiple and is spaced along the second circumferential direction, and overheating hole is used to conduct heat;Wherein, the diameter of second circumferential is greater than the diameter of first circumferential.The ceramic heat-insulating pipe provided in the present application, through hole is arranged on pipe body, heat is conducted by overheating hole, can reduce the temperature difference between fluid and pipe body, improve the life of pipe body;So that the temperature of pipe body rises, solidified fluid in central passage is melted again, restores the fluidity of fluid;Metal rod is arranged on pipe body, metal rod is heated by induction, indirectly heats the solidified fluid in central passage, restores the fluidity of fluid.

Description

Technical Field

[0001] This invention relates to the field of composite ceramic materials technology, and more specifically, to a ceramic insulation pipe and its preparation method. Background Technology

[0002] Currently, energy-efficient smelting furnaces concentrate molten aluminum by tilting the furnace, melting the input waste materials, thus reducing natural gas consumption. Traditional pipelines are unsuitable for this process. Using traditional pipelines leads to significant heat loss, is prone to blockages in practical applications, necessitating the repair and reinstallation of new pipelines, resulting in low efficiency in molten aluminum transfer. Summary of the Invention

[0003] The first aspect of the present invention provides a ceramic heat-insulating pipe to solve the technical problem that the use of traditional pipes in the prior art easily leads to large heat loss, easy blockage in actual application, and necessitates the destruction of the pipe and the reinstallation of a new pipe, resulting in low aluminum liquid transmission efficiency.

[0004] A first aspect of the present invention provides a ceramic heat-insulating pipe, comprising a pipe body having a central channel for conveying fluid; the pipe body having through holes and superheating holes, the through holes having a plurality of holes spaced apart along a first circumferential direction, a metal rod being fixedly disposed within the through holes, the metal rod being capable of induction heating; the superheating holes having a plurality of holes spaced apart along a second circumferential direction, the superheating holes being used for conducting heat; wherein the diameter of the second circumference is larger than the diameter of the first circumference.

[0005] This invention provides a ceramic heat-insulating pipe. In one embodiment, superheating holes are provided on the pipe body to conduct heat. This reduces the temperature difference between the fluid and the pipe body, extending the lifespan of the pipe body. Furthermore, it raises the temperature of the pipe body, causing the fluid solidified in the central channel to melt again and restore its fluidity. In another embodiment, a metal rod is provided on the pipe body. Induction heating of the metal rod indirectly heats the solidified fluid in the central channel, restoring its fluidity. Induction heating offers rapid heating, improving fluid flow efficiency. It is also clean and pollution-free, contributing to environmental protection. Moreover, by providing superheating holes and a metal rod on the pipe body, one or both heating methods can be selected, providing redundancy and preventing the fluid from solidifying in the central channel for an extended period due to a malfunction in either method, thus affecting fluid transport efficiency.

[0006] Furthermore, an induction coil is fitted on the outer circumferential surface of the tube body. The induction coil can be electrically connected to a power source. The power source provides alternating current to the induction coil to form an alternating magnetic field, which causes the metal rod to generate eddy currents to directly heat the fluid.

[0007] Furthermore, the metal rod is made of tungsten steel.

[0008] Furthermore, the end of the metal rod extends beyond the outer end face of the through hole, and a threaded portion is provided on the outer circumferential surface of the metal rod near the end. The threaded portion is connected to the tube body via a nut. This configuration, using a threaded connection, simplifies installation.

[0009] Furthermore, the outer circumferential surface of the metal rod within the through hole is provided with multiple raised ribs spaced apart along the circumferential direction. This arrangement, with multiple radiating ribs, facilitates rapid heat dissipation and improves the heating efficiency of the fluid within the central channel.

[0010] Furthermore, the pipe body is made of the following raw materials by mass percentage: 70%–75% Al2O3, 23.5%–28.5% SiC, and 0.5%–1.5% MgO. This arrangement ensures the pipe body has sufficient strength by increasing the proportion of Al2O3, improves its toughness and insulation by adding a certain amount of SiC, and enhances its density by adding a certain amount of MgO.

[0011] Furthermore, the tube body comprises, in a radially outward direction, an inner ceramic layer, a middle ceramic layer, and an outer ceramic layer, wherein the inner wall surface of the inner ceramic layer forms the central channel; the through hole is disposed in the inner ceramic layer; and the superheating hole is disposed in the outer ceramic layer.

[0012] Furthermore, the inner ceramic layer is made of the following raw materials by mass percentage: 70%–80% Al2O3, 18.5%–29.5% SiC, and 0.5%–1.5% MgO;

[0013] And / or, the intermediate ceramic layer is made of the following raw materials by mass percentage: 50%–60% Al2O3, 37%–49% SiC and 1%–3% MgO;

[0014] And / or, the outer ceramic layer is made of the following raw materials in weight percentages: 92.5%–95.5% Al2O3, 4%–6% SiC and 0.5%–1.5% MgO.

[0015] This invention provides a ceramic insulation pipe in which the inner, middle, and outer ceramic layers have different mass percentages of Al2O3, SiC, and MgO. Since the inner ceramic layer is in direct contact with the fluid, it needs to balance high-temperature resistance and strength. A SiC mass percentage between 18.5% and 29.5% meets this requirement. Because higher SiC content results in lower ceramic density, MgO acts as a binder, filling voids and improving the density of the inner ceramic layer. A MgO mass percentage between 0.5% and 1.5% meets this requirement. Since the middle ceramic layer is protected by the inner and outer layers, strength is secondary; the primary consideration is insulation. Therefore, the middle ceramic layer has a higher SiC mass percentage than the inner ceramic layer. The mass percentage of SiC is between 37% and 49%, which leads to a decrease in the density of the middle ceramic layer. Therefore, the proportion of MgO is increased, with the mass percentage of MgO between 1% and 3%. Since the outer ceramic layer is mainly designed for strength and thermal insulation is secondary, a low proportion of SiC is selected, with the mass percentage of SiC between 4% and 6%. At this point, the ceramic density is relatively high, and a low proportion of MgO is selected, with the mass percentage of MgO between 0.5% and 1.5%.

[0016] Furthermore, the diameter of the central channel is between 145mm and 155mm; and / or, the thickness of the inner ceramic layer is between 8mm and 12mm; and / or, the thickness of the middle ceramic layer is between 25mm and 35mm; and / or, the thickness of the outer ceramic layer is between 55mm and 65mm; and / or, the diameter of the through hole is between 12mm and 18mm; and / or, the diameter of the superheating hole is between 25mm and 35mm.

[0017] A second aspect of the present invention provides a method for preparing a ceramic insulation pipe, applicable to the ceramic insulation pipe described above, comprising the following steps:

[0018] Preparation of aluminum alloy casting rods: Prepare one first aluminum alloy casting rod with the same diameter as the central channel, multiple second aluminum alloy casting rods with the same diameter as the through hole, and multiple third aluminum alloy casting rods with the same diameter as the superheating hole.

[0019] Pretreatment of aluminum alloy casting rods: The first aluminum alloy casting rod, the second aluminum alloy casting rod, and the third aluminum alloy casting rod are heated at 545℃±5℃ for 1.5h-2.5h and then water-quenched, followed by artificial aging treatment at 190℃±5℃ for 2.5h-3.5h.

[0020] Preparation of the tube body: The first aluminum alloy cast rod, the second aluminum alloy cast rod, and the third aluminum alloy cast rod are placed in the mold according to the preset position; 70%-75% Al2O3, 23.5%-28.5% SiC, and 0.5%-1.5% MgO by mass percentage are mixed with water to form a slurry, which is poured into the mold. The slurry is statically pressed into shape under a pressure of 280MPa-300MPa. After air drying, it is pressure-free fired in a nitrogen atmosphere for 3-4 hours. The first aluminum alloy cast rod, the second aluminum alloy cast rod, and the third aluminum alloy cast rod all melt and flow out. After demolding, the tube body is obtained.

[0021] A third aspect of the present invention provides a method for preparing a ceramic insulation pipe, applicable to the ceramic insulation pipe described above, comprising the following steps:

[0022] Preparation of aluminum alloy casting rods: Prepare one first aluminum alloy casting rod with the same diameter as the central channel, multiple second aluminum alloy casting rods with the same diameter as the through hole, and multiple third aluminum alloy casting rods with the same diameter as the superheating hole.

[0023] Pretreatment of aluminum alloy casting rods: The first aluminum alloy casting rod, the second aluminum alloy casting rod, and the third aluminum alloy casting rod are heated at 545℃±5℃ for 1.5h-2.5h and then water-quenched, followed by artificial aging treatment at 190℃±5℃ for 2.5h-3.5h.

[0024] Preparation of the inner ceramic layer: The first aluminum alloy casting rod is placed in the first mold at a preset position. 70%-80% Al2O3, 18.5%-29.5% SiC and 0.5%-1.5% MgO are mixed with water to form a first slurry, which is then poured into the first mold. The first slurry is statically pressed into shape under a pressure of 280MPa-300MPa. After air drying, it is demolded to obtain the inner ceramic layer and the first aluminum alloy casting rod.

[0025] Preparation of the middle ceramic layer: The inner ceramic layer and the second aluminum alloy casting rod are placed in the second mold according to the preset position, and 50%-60% Al2O3, 37%-49% SiC and 1%-3% MgO by mass percentage are mixed with water to form a second slurry, which is poured into the second mold. The second slurry is statically pressed into shape under a pressure of 280MPa-300MPa. After air drying, the inner ceramic layer, the first aluminum alloy casting rod, the middle ceramic layer and the second aluminum alloy casting rod are obtained by demolding.

[0026] Preparation of the outer ceramic layer: The inner ceramic layer, the middle ceramic layer, and the third aluminum alloy casting rod are placed in a third mold according to a preset position. A third slurry is prepared by mixing 92.5%-95.5% Al2O3, 4%-6% SiC, and 0.5%-1.5% MgO by mass percentage with water and pouring it into the third mold. The third slurry is statically pressed into shape under a pressure of 280MPa-300MPa. After air drying, it is pressure-free fired in a nitrogen atmosphere for 2.5h-3.5h. The first aluminum alloy casting rod, the second aluminum alloy casting rod, and the third aluminum alloy casting rod all melt and flow out. After demolding, the composite of the inner ceramic layer, the middle ceramic layer, and the outer ceramic layer is obtained. Attached Figure Description

[0027] Figure 1 A cross-sectional view of a ceramic heat-insulating pipe provided in an embodiment of the present invention;

[0028] Figure 2 for Figure 1 Enlarged structural diagram at point A in the middle;

[0029] Explanation of reference numerals in the attached figures:

[0030] 1 – Central channel; 2 – Inner ceramic layer; 3 – Middle ceramic layer; 4 – Through hole; 5 – Metal rod; 6 – Overheating hole; 7 – Outer ceramic layer; 8 – Induction coil. Detailed Implementation

[0031] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the following description is provided in conjunction with the accompanying drawings. Figure 1 —2. Specific embodiments of the present invention will be described in detail.

[0032] A first aspect of the present invention provides a ceramic heat-insulating pipe, see attached figure. Figure 1 The ceramic insulation pipe includes a pipe body with a central channel 1 for conveying fluid; the pipe body is provided with through holes 4 and superheating holes 6. There are multiple through holes 4 and they are spaced apart along a first circumferential direction. A metal rod 5 is fixed inside the through hole 4 and the metal rod 5 can be heated by induction; there are multiple superheating holes 6 and they are spaced apart along a second circumferential direction. The superheating holes 6 are used to conduct heat; wherein the diameter of the second circumference is larger than the diameter of the first circumference.

[0033] An embodiment of the present invention provides a ceramic insulation pipe with the following application scenario: the fluid is molten aluminum; the ceramic insulation pipe includes a first ceramic insulation pipe and a second ceramic insulation pipe; one end of the first ceramic insulation pipe has an overheating hole 6 and a central channel 1 connected to a smelting furnace, and the other end of the first ceramic insulation pipe has a central channel 1 connected to the input end of an aluminum molten pump; one end of the second ceramic insulation pipe has a central channel 1 connected to the output end of an aluminum molten pump, and the other end of the second ceramic insulation pipe has an overheating hole 6 and a central channel 1 connected to a settling furnace, thereby enabling the molten aluminum in the smelting furnace to be poured into the settling furnace, avoiding the introduction of air to form slag and avoiding heat loss.

[0034] It should be noted that the tube body is made of ceramic material, and the molten aluminum flows in the central channel 1. The ceramic material of the tube body provides good heat preservation.

[0035] The superheating hole 6 connects the smelting furnace and the settling furnace. The excess heat from the smelting furnace and the settling furnace will continuously heat the tube body. Even if the aluminum liquid pump is not working, the heat can be conducted through the superheating hole 6 to maintain the temperature of the tube body. In this way, when the aluminum liquid pump is initially turned on, the tube body will not be shortened due to the large temperature difference between the aluminum liquid and the tube body.

[0036] During the process of pouring molten aluminum from the smelting furnace into the settling furnace, the molten aluminum pump may malfunction or cause other reasons, resulting in the molten aluminum in the ceramic insulation pipe stopping its flow and solidifying inside the pipe. In one embodiment, the natural gas heating of the smelting furnace and the settling furnace can be started to raise the temperature inside the furnace. The excess heat is conducted through the superheating hole 6, which raises the temperature of the pipe body. Generally, after 20-30 minutes, the aluminum melts again, restoring the fluidity of the molten aluminum. In another embodiment, the metal rod 5 can be heated by induction heating to indirectly heat the aluminum in the central channel 1. Since the metal rod 5 is closer to the central channel 1, it generally only takes 5-10 minutes for the aluminum to melt again, restoring the fluidity of the molten aluminum.

[0037] Therefore, the ceramic insulation pipe provided in this embodiment of the invention has two implementations. In one implementation, a superheating hole 6 is provided on the pipe body. Heat is conducted through the superheating hole 6, which on the one hand reduces the temperature difference between the fluid and the pipe body, thus extending the life of the pipe body; on the other hand, it raises the temperature of the pipe body, causing the fluid solidified in the central channel 1 to melt again and restore the fluid's fluidity. In another implementation, a metal rod 5 is provided on the pipe body. The solidified fluid in the central channel 1 is indirectly heated by induction heating of the metal rod 5, restoring the fluid's fluidity. On the one hand, induction heating has a fast heating speed, improving fluid flow efficiency; on the other hand, induction heating is clean and pollution-free, helping to protect the environment. In addition, by providing the superheating hole 6 and the metal rod 5 on the pipe body, one heating method or two heating methods can be selected simultaneously, providing redundancy and preventing the fluid from solidifying in the central channel 1 for a long time due to the failure of one method, thus affecting the fluid transmission efficiency. Simultaneously selecting two heating methods can achieve rapid heating.

[0038] In this embodiment of the invention, the through holes 4 are evenly spaced along the first circumferential direction. Preferably, the number of through holes 4 is 8.

[0039] In this embodiment of the invention, the superheating holes 6 are evenly spaced along the second circumferential direction. Preferably, the number of superheating holes 6 is 8.

[0040] Embodiments of the present invention are shown in the appendix. Figure 1 An induction coil 8 is fitted on the outer circumference of the tube body. The induction coil 8 can be electrically connected to a power source. The power source provides alternating current to the induction coil 8 to form an alternating magnetic field, which causes the metal rod 5 to generate eddy currents and directly heat the fluid.

[0041] In this embodiment of the invention, the metal rod 5 is made of tungsten steel.

[0042] It should be noted that tungsten steel can withstand temperatures above 3000℃.

[0043] Preferably, the tungsten steel is W18Cr4V steel.

[0044] In this embodiment of the invention, the end of the metal rod 5 extends beyond the outer end face of the through hole 4, and a threaded portion is provided on the outer circumferential surface of the metal rod 5 near the end. The threaded portion is connected to the tube body by a nut. This configuration, using a threaded connection, simplifies the installation process.

[0045] Embodiments of the present invention are shown in the appendix. Figure 2 The metal rod 5 has raised ribs on its outer circumferential surface inside the through hole 4. There are multiple raised ribs spaced apart along the circumferential direction. This arrangement, with multiple radiating raised ribs, facilitates rapid heat dissipation and improves the heating efficiency of the fluid in the central channel 1.

[0046] In this embodiment of the invention, the tube body is made of Al2O3 ceramic.

[0047] It should be noted that the tube body is made of Al2O3 ceramic, which is a ceramic material with alumina as the main component. Al2O3 ceramic has good conductivity, mechanical strength and high temperature resistance.

[0048] In this embodiment of the invention, the tube body is made of the following raw materials in the indicated mass percentages: 70%–75% Al2O3, 23.5%–28.5% SiC, and 0.5%–1.5% MgO.

[0049] The ceramic insulation pipe provided in this embodiment of the invention improves the toughness of Al2O3 ceramics and enhances its insulation properties by adding a certain amount of SiC to Al2O3 ceramics; and by adding a certain amount of MgO to reduce the porosity of Al2O3 ceramics and improve their density.

[0050] Therefore, the ceramic insulation pipe provided in this embodiment of the invention has a higher proportion of Al2O3 to ensure that the pipe body has a certain strength, adds a certain amount of SiC to improve the toughness and insulation of the pipe body, and adds a certain amount of MgO to improve the density of the pipe body.

[0051] Embodiments of the present invention are shown in the appendix. Figure 1 The tube body includes, in a radial outward direction, an inner ceramic layer 2, a middle ceramic layer 3, and an outer ceramic layer 7. The inner wall surface of the inner ceramic layer 2 forms a central channel 1. A through hole 4 is provided in the inner ceramic layer 2. A superheating hole 6 is provided in the outer ceramic layer 7.

[0052] In this embodiment of the invention, the inner ceramic layer 2 is made of the following raw materials in the following mass percentages: 70%–80% Al2O3, 18.5%–29.5% SiC, and 0.5%–1.5% MgO. Since the inner ceramic layer 2 is in direct contact with the fluid, it needs to balance high-temperature resistance and strength. Setting the mass percentage of SiC between 18.5% and 29.5% meets the requirements. Because the higher the SiC content, the lower the ceramic density, MgO acts as a binder, filling the voids and improving the density of the inner ceramic layer. Setting the mass percentage of MgO between 0.5% and 1.5% meets the requirements.

[0053] In this embodiment of the invention, the middle ceramic layer 3 is made of the following raw materials by mass percentage: 50%-60% Al2O3, 37%-49% SiC, and 1%-3% MgO. Since the middle ceramic layer is protected by the inner and outer ceramic layers, strength is secondary; the primary consideration is thermal insulation. Therefore, compared to the inner ceramic layer 2, the mass percentage of SiC in the middle ceramic layer 3 is higher than that in the inner ceramic layer, ranging from 37% to 49%. This results in a decrease in the ceramic density of the middle ceramic layer 3, thus increasing the proportion of MgO, which ranges from 1% to 3% by mass.

[0054] In this embodiment of the invention, the outer ceramic layer 7 is made of the following raw materials by mass percentage: 92.5%–95.5% Al₂O₃, 4%–6% SiC, and 0.5%–1.5% MgO. Since the outer ceramic layer 7 primarily considers strength, and thermal insulation is secondary, a low proportion of SiC is selected, with the SiC mass percentage between 4% and 6%, resulting in higher ceramic density. A low proportion of MgO is also chosen, with the MgO mass percentage between 0.5% and 1.5%.

[0055] In this embodiment of the invention, the diameter of the central channel 1 is between 145mm and 155mm.

[0056] In this embodiment of the invention, the thickness of the inner ceramic layer 2 is between 8mm and 12mm.

[0057] In this embodiment of the invention, the thickness of the middle ceramic layer 3 is between 25mm and 35mm.

[0058] In this embodiment of the invention, the thickness of the outer ceramic layer 7 is between 55mm and 65mm.

[0059] In this embodiment of the invention, the diameter of the through hole 4 is between 12mm and 18mm.

[0060] In this embodiment of the invention, the diameter of the superheating hole 6 is between 25mm and 35mm.

[0061] A second aspect of this invention provides a method for preparing a ceramic insulation pipe, applicable to the aforementioned ceramic insulation pipe, comprising the following steps:

[0062] Preparation of aluminum alloy casting rods: Prepare one first aluminum alloy casting rod with the same diameter as the central channel 1, multiple second aluminum alloy casting rods with the same diameter as the through hole 4, and multiple third aluminum alloy casting rods with the same diameter as the superheated hole 6.

[0063] Pretreatment of aluminum alloy cast rods: The first aluminum alloy cast rod, the second aluminum alloy cast rod, and the third aluminum alloy cast rod are heated at 545℃±5℃ for 1.5h-2.5h and then water-quenched, followed by artificial aging treatment at 190℃±5℃ for 2.5h-3.5h.

[0064] Preparation of the tube body: The first aluminum alloy cast rod, the second aluminum alloy cast rod, and the third aluminum alloy cast rod are placed in the mold according to the preset position; 70%-75% Al2O3, 23.5%-28.5% SiC, and 0.5%-1.5% MgO by mass percentage are mixed with water to form a slurry, which is poured into the mold. The slurry is statically pressed into shape under a pressure of 280MPa-300MPa. After air drying, it is pressureless fired in a nitrogen atmosphere for 3-4 hours. The first aluminum alloy cast rod, the second aluminum alloy cast rod, and the third aluminum alloy cast rod all melt and flow out. After demolding, the tube body is obtained.

[0065] A third aspect of this invention provides a method for preparing a ceramic insulation pipe, applicable to the aforementioned ceramic insulation pipe, comprising the following steps:

[0066] Preparation of aluminum alloy casting rods: Prepare one first aluminum alloy casting rod with the same diameter as the central channel 1, multiple second aluminum alloy casting rods with the same diameter as the through hole 4, and multiple third aluminum alloy casting rods with the same diameter as the superheated hole 6.

[0067] Pretreatment of aluminum alloy cast rods: The first aluminum alloy cast rod, the second aluminum alloy cast rod, and the third aluminum alloy cast rod are heated at 545℃±5℃ for 1.5h-2.5h and then water-quenched, followed by artificial aging treatment at 190℃±5℃ for 2.5h-3.5h.

[0068] Preparation of inner ceramic layer 2: The first aluminum alloy casting rod is placed in the first mold at a preset position. 70%-80% Al2O3, 18.5%-29.5% SiC and 0.5%-1.5% MgO are mixed with water to form a first slurry, which is poured into the first mold. The first slurry is statically pressed into shape under a pressure of 280MPa-300MPa. After air drying, it is demolded to obtain inner ceramic layer 2 and the first aluminum alloy casting rod.

[0069] Preparation of the middle ceramic layer 3: The inner ceramic layer 2 and the second aluminum alloy cast rod are placed in the second mold according to the preset position, and 50%-60% Al2O3, 37%-49% SiC and 1%-3% MgO by mass percentage are mixed with water to form a second slurry, which is poured into the second mold. The second slurry is statically pressed into shape under a pressure of 280MPa-300MPa. After air drying, it is demolded to obtain the inner ceramic layer 2, the first aluminum alloy cast rod, the middle ceramic layer 3 and the second aluminum alloy cast rod.

[0070] Preparation of outer ceramic layer 7: Inner ceramic layer 2, middle ceramic layer 3 and third aluminum alloy cast rod are placed in the third mold according to the preset position. A third slurry is prepared by mixing 92.5%-95.5% Al2O3, 4%-6% SiC and 0.5%-1.5% MgO by mass percentage with water and pouring it into the third mold. The third slurry is statically pressed into shape under a pressure of 280MPa-300MPa. After air drying, it is pressure-free fired in a nitrogen atmosphere for 2.5h-3.5h. The first aluminum alloy cast rod, the second aluminum alloy cast rod and the third aluminum alloy cast rod melt and flow out. After demolding, the composite of inner ceramic layer 2, middle ceramic layer 3 and outer ceramic layer 7 is obtained.

[0071] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A ceramic heat-insulating pipe, characterized in that, The device includes a pipe body having a central channel (1) for conveying fluid; the pipe body is provided with through holes (4) and superheating holes (6); the through holes (4) are multiple and spaced apart along a first circumferential direction; a metal rod (5) is fixed inside the through holes (4) and the metal rod (5) is capable of induction heating; the superheating holes (6) are multiple and spaced apart along a second circumferential direction and are used for conducting heat; wherein the diameter of the second circumference is larger than the diameter of the first circumference.

2. The ceramic heat-insulating pipe according to claim 1, characterized in that, An induction coil (8) is fitted on the outer circumference of the tube body. The induction coil (8) can be electrically connected to a power source. The power source provides alternating current to the induction coil (8) to form an alternating magnetic field, which causes the metal rod (5) to generate eddy currents and directly heat the fluid.

3. The ceramic heat-insulating pipe according to claim 1, characterized in that, The metal rod (5) is made of tungsten steel; And / or, the end of the metal rod (5) extends out of the outer end face of the through hole (4), and the outer circumferential surface of the metal rod (5) near the end is provided with a threaded part, which is connected to the tube body by a nut; And / or, the outer circumferential surface of the metal rod (5) located in the through hole (4) is provided with a protrusion, and the number of the protrusions is multiple and they are spaced apart along the circumferential direction.

4. The ceramic heat-insulating pipe according to any one of claims 1-3, characterized in that, The tube body is made of the following raw materials in the following mass percentages: 70%–75% Al2O3, 23.5%–28.5% SiC and 0.5%–1.5% MgO.

5. The ceramic insulation pipe according to any one of claims 1-3, characterized in that, The tube body comprises, in a radial outward direction, an inner ceramic layer (2), a middle ceramic layer (3), and an outer ceramic layer (7). The inner wall surface of the inner ceramic layer (2) forms the central channel (1). The through hole (4) is provided in the inner ceramic layer (2). The superheating hole (6) is provided in the outer ceramic layer (7).

6. The ceramic insulation pipe according to claim 5, characterized in that, The inner ceramic layer (2) is made of the following raw materials in the following mass percentages: 70%-80% Al2O3, 18.5%-29.5% SiC and 0.5%-1.5% MgO; And / or, the intermediate ceramic layer (3) is made of the following raw materials by mass percentage: 50%-60% Al2O3, 37%-49% SiC and 1%-3% MgO; And / or, the outer ceramic layer (7) is made of the following raw materials in the following mass percentages: 92.5%–95.5% Al2O3, 4%–6% SiC and 0.5%–1.5% MgO.

7. The ceramic insulation pipe according to claim 5, characterized in that, The diameter of the central channel (1) is between 145mm and 155mm; and / or, the thickness of the inner ceramic layer (2) is between 8mm and 12mm; and / or, the thickness of the middle ceramic layer (3) is between 25mm and 35mm; and / or, the thickness of the outer ceramic layer (7) is between 55mm and 65mm; and / or, the diameter of the through hole (4) is between 12mm and 18mm; and / or, the diameter of the superheating hole (6) is between 25mm and 35mm.

8. A method for preparing a ceramic heat-insulating pipe, characterized in that, The method applied to the ceramic insulation pipe according to any one of claims 1-4 includes the following steps: Preparation of aluminum alloy casting rods: Prepare one first aluminum alloy casting rod with the same diameter as the central channel (1), multiple second aluminum alloy casting rods with the same diameter as the through hole (4), and multiple third aluminum alloy casting rods with the same diameter as the overheating hole (6). Pretreatment of aluminum alloy casting rods: The first aluminum alloy casting rod, the second aluminum alloy casting rod, and the third aluminum alloy casting rod are heated at 545℃±5℃ for 1.5h-2.5h and then water-quenched, followed by artificial aging treatment at 190℃±5℃ for 2.5h-3.5h. Preparation of the tube body: The first aluminum alloy cast rod, the second aluminum alloy cast rod, and the third aluminum alloy cast rod are placed in the mold at preset positions; 70%-75% Al2O3, 23.5%-28.5% SiC, and 0.5%-1.5% MgO by mass percentage are mixed with water to form a slurry, which is then poured into the mold. The slurry is statically pressed into shape under a pressure of 280MPa-300MPa. After air drying, it is pressure-free fired in a nitrogen atmosphere for 3-4 hours. The first aluminum alloy cast rod, the second aluminum alloy cast rod, and the third aluminum alloy cast rod all melt and flow out. After demolding, the tube body is obtained.

9. A method for preparing a ceramic heat-insulating pipe, characterized in that, The ceramic insulation pipe applied to any one of claims 5-7 comprises the following steps: Preparation of aluminum alloy casting rods: Prepare one first aluminum alloy casting rod with the same diameter as the central channel (1), multiple second aluminum alloy casting rods with the same diameter as the through hole (4), and multiple third aluminum alloy casting rods with the same diameter as the overheating hole (6). Pretreatment of aluminum alloy casting rods: The first aluminum alloy casting rod, the second aluminum alloy casting rod, and the third aluminum alloy casting rod are heated at 545℃±5℃ for 1.5h-2.5h and then water-quenched, followed by artificial aging treatment at 190℃±5℃ for 2.5h-3.5h. Preparation of inner ceramic layer (2): The first aluminum alloy casting rod is placed in the first mold at a preset position. 70%-80% Al2O3, 18.5%-29.5% SiC and 0.5%-1.5% MgO are mixed with water to form a first slurry, which is poured into the first mold. The first slurry is statically pressed into shape under a pressure of 280MPa-300MPa. After air drying, the inner ceramic layer (2) and the first aluminum alloy casting rod are obtained by demolding. Preparation of the middle ceramic layer (3): The inner ceramic layer (2) and the second aluminum alloy casting rod are placed in the second mold at a preset position, and 50%-60% Al2O3, 37%-49% SiC and 1%-3% MgO by mass percentage are mixed with water to form a second slurry and poured into the second mold. The second slurry is statically pressed into shape under a pressure of 280MPa-300MPa. After air drying, the inner ceramic layer (2), the first aluminum alloy casting rod, the middle ceramic layer (3) and the second aluminum alloy casting rod are obtained by demolding. Preparation of the outer ceramic layer (7): The inner ceramic layer (2), the middle ceramic layer (3) and the third aluminum alloy casting rod are placed in the third mold at a preset position. The third slurry is made by mixing 92.5%-95.5% Al2O3, 4%-6% SiC and 0.5%-1.5% MgO with water by mass percentage and poured into the third mold. The third slurry is statically pressed into shape under a pressure of 280MPa-300MPa. After air drying, it is pressure-free fired in a nitrogen atmosphere for 2.5h-3.5h. The first aluminum alloy casting rod, the second aluminum alloy casting rod and the third aluminum alloy casting rod melt and flow out. After demolding, the composite of the inner ceramic layer (2), the middle ceramic layer (3) and the outer ceramic layer (7) is obtained.

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