Heat preservation device and expanding equipment
By installing an insulating shell on the mid-frequency induction heating coil jacket and using the reflective layer to reflect heat, the problem of heat loss of the mid-frequency induction heating coil is solved, and efficient steel pipe heating and stable quality thermal expansion process is achieved.
Patent Information
- Application Number
- CN202422356968.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-26
- Publication Date
- 2025-08-22
- Estimated Expiration
- 2034-09-26
AI Technical Summary
The existing medium frequency induction heating coils have severe heat loss during the thermal expansion of seamless steel pipes, resulting in high energy consumption and long time, and increasing production costs.
A thermal insulation device is designed, including an insulation shell mounted outside the thermal expansion tube and the induction heating coil, reflecting heat through a specific structure and reflecting layer, reducing heat loss and improving heating efficiency.
Effectively prevent heat from being dispersed to the surrounding environment, improve heating efficiency, reduce production costs, improve operating environment, and ensure steel pipe quality and yield.
Smart Images
Figure CN223250373U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the technical field of thermal expansion of steel pipes, in particular to a heat preservation device and expansion equipment. Background Art
[0002] During the medium-frequency induction heat expansion process for seamless steel pipes, the raw material mother pipe is placed in a medium-frequency induction coil for heating. When the mother pipe reaches the specified deformation temperature, the hydraulic cylinder piston pushes the mother pipe to expand its diameter using a tapered mandrel placed inside. The medium-frequency induction heating temperature is a key parameter for ensuring the quality of the heat-expanded steel pipe.
[0003] However, the medium-frequency induction heating coils used in existing technologies are exposed to the operating environment, which easily causes a large amount of heat loss. The energy consumption and time required to heat the steel pipe to the specified process temperature are high, which increases production costs. Utility Model Content
[0004] The purpose of the utility model is to provide a heat preservation device and a diameter expansion device to reduce the heat loss of the medium frequency induction heating coil, improve the heating efficiency of the steel pipe, and improve the working environment.
[0005] To achieve this purpose, the present invention adopts the following technical solutions:
[0006] A heat preservation device, comprising:
[0007] An insulating shell can be mounted outside the thermal expansion tube and the induction heating coil and spaced apart from the thermal expansion tube. The induction heating coil is located between the insulating shell and the thermal expansion tube. The insulating shell includes a first insulating section and a second insulating section that are connected. Along the axial direction of the thermal expansion tube, the inner diameter of the first insulating section gradually decreases in a direction away from the second insulating section, and the inner diameter of the second insulating section gradually decreases in a direction away from the first insulating section.
[0008] As an optional solution for the insulation device, the thermal expansion tube includes an introduction section, a deformation section and a sizing section arranged in sequence, the first insulation section covers the deformation section and part of the introduction section, and the second insulation section covers part of the sizing section.
[0009] As an optional solution of the heat preservation device, the first heat preservation section forms an angle A1 with the axis m of the thermal expansion tube, and the deformation section forms an angle A3 with the axis m, where A1=A3.
[0010] As an optional solution of the heat preservation device, the second heat preservation section forms an angle A2 with the axis m, where A1 = A2.
[0011] As an optional solution of the insulation device, the insulation device also includes a reflection ring, and the reflection ring is provided at at least one end of the insulation shell, the heat expansion tube is passed through the reflection ring, and the reflection ring is configured to reflect the heat in the gap between the insulation shell and the heat expansion tube.
[0012] As an optional solution for the thermal insulation device, the reflective ring includes a reflective surface and a through hole arranged on the reflective surface, the thermal expansion tube is passed through the through hole, and the reflective surface is inclined from the direction away from the thermal insulation shell to the direction close to the thermal expansion tube.
[0013] As an optional solution for the heat-insulating device, the reflective rings are provided at both ends of the heat-insulating shell, and the inclination angles of the two reflective rings are equal.
[0014] As an optional solution of the heat preservation device, the heat expansion tube includes a deformation section, and the angle between the reflecting surface and the axis m of the heat expansion tube is greater than the angle A3 between the deformation section and the axis m.
[0015] As an optional solution of the heat insulation device, the heat insulation device further includes a reflective layer, which is arranged on the inner wall of the heat insulation shell, and the reflective layer is configured to reflect heat radiation to the heat expansion tube.
[0016] A diameter expansion device comprises a conical core rod and an induction heating coil, wherein the conical core rod is configured to pass through a heat expansion tube, the induction heating coil is sleeved outside the heat expansion tube to heat the heat expansion tube, and the heat preservation device is included.
[0017] Beneficial effects:
[0018] The purpose of this solution is to provide a heat-insulating device and a diameter-expanding device, wherein the heat-insulating outer shell of the heat-insulating device is sleeved outside the heat-expanding tube and spaced apart from the heat-expanding tube, and the induction heating coil is located between the heat-insulating outer shell and the heat-expanding tube, so that the heat-insulating outer shell can effectively prevent heat from being dissipated to the surrounding environment. Moreover, since the inner diameter of the first heat-insulating section gradually decreases in the direction away from the second heat-insulating section along the axial direction of the heat-expanding tube, and the inner diameter of the second heat-insulating section gradually decreases in the direction away from the first heat-insulating section, the heat-insulating outer shell has a closed structure at both ends along the axial direction of the heat-expanding tube, which not only reduces the efficiency of heat exchange between the inside and outside of the heat-insulating outer shell, but also can reflect convection and heat radiation toward the direction of the heat-expanding tube, reducing heat loss, improving heat utilization, and thus improving heating efficiency. BRIEF DESCRIPTION OF THE DRAWINGS
[0019] Figure 1 This is a perspective view of a heat preservation device and a diameter expansion device provided by an embodiment of the present utility model;
[0020] Figure 2 It is a cross-sectional view of the heat preservation device provided by an embodiment of the present utility model.
[0021] In the picture:
[0022] 1-insulation shell; 11-first insulation section; 12-second insulation section; 13-reflection ring; 14-reflection layer; 15-protective layer; 131-first reflection ring; 132-second reflection ring; 141-first reflection layer; 142-second reflection layer;
[0023] 2-thermal expansion section; 21-introduction section; 22-deformation section; 23-sizing section;
[0024] 3- Induction heating coil. DETAILED DESCRIPTION
[0025] The present invention will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are intended only to illustrate the present invention and are not intended to limit the present invention. It should also be noted that, for ease of description, the accompanying drawings only illustrate portions relevant to the present invention, not all of its components.
[0026] In the description of this utility model, unless otherwise specified or limited, the terms "connected," "connect," and "fixed" should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integration; mechanical connection or electrical connection; direct connection or indirect connection through an intermediate medium; internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in this utility model based on the specific circumstances.
[0027] In the present invention, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Moreover, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being directly below or obliquely below the second feature, or may simply mean that the first feature is lower in level than the second feature.
[0028] In the description of this embodiment, the terms "upper" and "lower" and other orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely for ease of description and simplified operation. They do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. Furthermore, the terms "first" and "second" are used solely for descriptive distinction and do not have any special meaning.
[0029] Medium frequency heat expansion process is a common method for producing large diameter seamless steel pipes. This process requires the use of expansion equipment to achieve the expansion operation of the steel pipe. Figure 1 As shown, this embodiment provides a diameter expansion device, which includes a conical mandrel and an induction heating coil 3. The conical mandrel is configured to pass through the steel pipe, and the induction heating coil 3 is sleeved outside the steel pipe to heat the steel pipe.
[0030] The process principle of medium-frequency thermal expansion is to heat the steel pipe through the induction heating coil 3. At the same time, under the push of the hydraulic cylinder piston, the steel pipe is expanded with the help of the conical mandrel placed inside it. Among them, the steel pipe that needs to be expanded is called the thermal expansion pipe 2. During the thermal expansion process, the part of the thermal expansion pipe 2 where the diameter remains unchanged is the introduction section 21, the part where the thermal expansion pipe 2 and the conical surface of the conical mandrel contact each other is the deformation section 22, and the part where the thermal expansion pipe 2 is fully expanded is the sizing section 23. In the existing technology, the induction heating coil 3 is exposed to the operating environment, which easily leads to a large amount of heat loss, resulting in high energy consumption and a long time required to heat the steel pipe to the specified process temperature, thereby increasing production costs.
[0031] To solve the above problems, this embodiment provides a heat preservation device, which is applied to the expansion process of steel pipes. Figure 1 As shown, the thermal insulation device includes an insulating outer shell 1, which can be mounted over a thermal expansion tube 2 and an induction heating coil 3, spaced apart from the thermal expansion tube 2. The induction heating coil 3 is located between the insulating outer shell 1 and the thermal expansion tube 2, with a radial distance of 80-100 mm from the outer surface of the thermal expansion tube 2. The insulating outer shell 1 effectively blocks heat dissipation to the surrounding environment and, by reducing heat dissipation through thermal radiation, effectively retains the heat generated by the induction heating coil 3, thereby improving heating efficiency.
[0032] Furthermore, the thermal insulation shell 1 includes a first thermal insulation section 11 and a second thermal insulation section 12 connected to each other. Along the axial direction of the thermal expansion tube 2, the inner diameter of the first thermal insulation section 11 gradually decreases in the direction away from the second thermal insulation section 12, and the inner diameter of the second thermal insulation section 12 gradually decreases in the direction away from the first thermal insulation section 11, so that both ends of the thermal insulation shell 1 along the axial direction of the thermal expansion tube 2 are closed structures. This special shape design better adapts to the shape of the thermal expansion tube 2, which not only reduces the efficiency of heat exchange between the inside and outside of the thermal insulation shell 1, but also can reflect convection and heat radiation toward the direction of the thermal expansion tube 2, reducing heat loss, improving heat utilization, and thus improving heating efficiency.
[0033] In this embodiment, the thermal insulation shell 1 is composed of a composite of multiple layers of materials. There are many ways to use and combine the materials of the thermal insulation shell 1, and there are no specific restrictions. It is worth noting that the structure of the thermal insulation shell 1 is to first coat it with 2-3 layers of nano aerogel insulation material, and each layer is wrapped and fixed with a stainless steel belt. The nano aerogel insulation material has extremely low thermal conductivity and can greatly reduce the conduction of heat. It is then coated with an aluminum silicate needle-punched blanket or high-temperature glass wool and wrapped and fixed with a stainless steel belt, which further enhances the thermal insulation effect and also plays a role in heat insulation. The structure of the thermal insulation shell 1 can prevent heat loss, thereby reducing the temperature of the working area, so that the external temperature of the thermal insulation shell 1 does not exceed 45 degrees Celsius, and improves the comfort and safety of the operator.
[0034] like Figure 1 As shown, the first insulation section 11 covers the deformation section 22 and part of the introduction section 21, and the second insulation section 12 covers part of the sizing section 23. On the one hand, the first insulation section 11 can provide a stable high-temperature environment for the deformation section 22, ensure the efficient thermal expansion and deformation, reduce the problem of uneven deformation caused by temperature fluctuations, and improve the quality of the thermal expansion tube 2. At the same time, covering part of the introduction section 21 helps the steel pipe to enter the deformation section 22 smoothly, reduces the stress concentration caused by temperature differences, and reduces the risk of defects such as cracks in the steel pipe when entering the deformation section 22. On the other hand, the second insulation section 12 covers part of the sizing section 23, which can maintain a certain temperature during the sizing process after thermal expansion, helps to control the dimensional accuracy and surface quality of the steel pipe, makes sizing more accurate, and improves the product yield and consistency.
[0035] Specifically, for the convenience of description, the intersection of the first insulation section 11 and the second insulation section 12 is defined as the waistline N. The insulation shell 1 is provided with an axis M in its axial direction, and the insulation shell 1 is axially symmetrically distributed along the axis M. Specifically, ignoring the installation errors caused by manual labor during the installation process, at this time, the intersection of the deformation section 22 and the sizing section 23 coincides with the waistline N, and the thermal expansion tube 2 is axially symmetrically distributed along the axis M, that is, the axis m of the thermal expansion tube 2 coincides with the axis M of the insulation shell 1. The maximum inner diameter of the insulation shell 1 at the waistline N position is the maximum outer diameter of the induction heating coil 3 plus 60-100 mm. This leaves a gap between the insulation shell 1 and the induction heating coil 3. On the one hand, it prevents the insulation shell 1 from being too close to the induction heating coil 3 and deforming due to heat, thereby ensuring the stability and reliability of the insulation device during the production of the thermal expansion tube 2. On the other hand, controlling the gap within an appropriate range can also effectively avoid cost waste and improve the economy of the production process.
[0036] The axial length L1 of the first insulation section 11 is 200-500 mm greater than the combined length of the lead-in section 21 and the deformation section 22, which are enclosed by the induction heating coil 3. The axial length L2 of the second insulation section 12 is 200-500 mm greater than the length of the sizing section 23, which is enclosed by the induction heating coil 3. This ensures a wide coverage area for the insulation device, completely encompassing the induction heating coil 3. This ensures a good preheating effect for the lead-in section 21 near the induction heating coil 3, effectively preventing the lead-in section 21 from being suddenly heated by the heating coil 3. It also allows the sizing section 23, which is separated from the heating coil 3, to cool slowly, effectively preventing the sizing section 23 from being suddenly exposed to the operating environment and causing a rapid temperature drop. This stable temperature prevents defects such as cracks from appearing on the steel pipe surface, thereby ensuring the quality of the thermally expanded pipe 2 and providing reliable support for its production.
[0037] Furthermore, the first insulation section 11 forms an angle A1 with the axis m of the thermal expansion tube 2, and the deformation section 22 forms an angle A3 with the axis m of the thermal expansion tube 2. Angle A1 is equal to angle A3, meaning that the inner wall of the first insulation section 11 is parallel to the outer wall of the deformation section 22. This structure better concentrates heat in the deformation section 22, improving energy efficiency and reducing energy consumption. Furthermore, the angle A1 is allowed to fluctuate within a range of 3-5 degrees, accounting for installation errors and manufacturing precision issues in actual production without significantly affecting the insulation effect, making the production process more flexible and feasible.
[0038] Furthermore, the second insulation section 12 forms an angle A2 with the axis m, A1=A2. According to the principle of mirror symmetry between the incident angle of thermal radiation and the reflection angle, the above structure can reflect most of the thermal radiation perpendicular to the axis m to the thermal expansion tube 2, so that the originally wasted thermal radiation can provide a heat source for the deformation section 22 again, which helps to maintain a stable high-temperature environment of the deformation section 22, ensure the efficient thermal expansion and deformation, and improve the energy utilization efficiency.
[0039] In some embodiments, the thermal insulation device further includes a reflective layer 14 disposed on the inner wall of the thermal insulation housing 1 and configured to reflect thermal radiation toward the thermal expansion tube 2. The reflective layer 14 is made of a high-reflectivity, high-temperature-resistant material, such as stainless steel. In this case, the inner wall roughness of the reflective layer 14 is no greater than 0.1 microns. The smooth inner wall enhances the reflective effect, preventing the thermal insulation housing 1 from absorbing thermal radiation. Instead, the reflective radiation is reflected back to the heat source, i.e., the thermal expansion tube 2, as much as possible, effectively reducing radiant heat loss.
[0040] like Figure 2For ease of description, the reflective layer 14 disposed on the inner wall of the first insulation section 11 is referred to as the first reflective layer 141, and the reflective layer 14 disposed on the inner wall of the second insulation section 12 is referred to as the second reflective layer 142. The first and second reflective layers 141, 142 are formed by rolling stainless steel sheets into conical cylinders and then welding them along the longitudinal seam. The first and second reflective layers 141, 142 are welded together along the butted circumferential seam to form a single unit and are welded to the inner wall of the insulation housing 1. The inner wall of the first reflective layer 141 is parallel to the inner wall of the first insulation section 11, and forms an angle A1 with the axis of the thermal expansion tube 2. The inner wall of the second reflective layer 142 is parallel to the inner wall of the second insulation section 12, and forms an angle A2 with the axis of the thermal expansion tube 2. Based on the principle of mirror symmetry between the incident angle and the reflection angle of thermal radiation, thermal radiation is reflected back to the deformation section 22 as much as possible, further improving heat utilization.
[0041] In some embodiments, the thermal insulation device further includes a protective layer 15, which is coated on the outside of the thermal insulation shell 1. The protective layer 15 is formed by rolling and welding aluminum or galvanized sheet, and effectively protects the thermal insulation shell 1. During actual use, the thermal insulation device may be exposed to various external impacts, friction, or corrosion, etc., and the protective layer 15 is used to prevent damage to the thermal insulation shell 1 from external factors, thereby extending the service life of the thermal insulation device.
[0042] In this embodiment, the insulation device also includes a reflection ring 13, and the reflection ring 13 is provided at at least one end of the insulation shell 1, and the thermal expansion tube 2 is passed through the reflection ring 13. The reflection ring 13 is configured to reflect the heat in the gap between the insulation shell 1 and the thermal expansion tube 2, reduce the radiation loss of heat to the external environment, and retain more heat in the area between the insulation shell 1 and the thermal expansion tube 2, thereby reducing energy waste.
[0043] Specifically, the reflection ring 13 includes a reflection surface and a through-hole provided on the reflection surface, and the thermal expansion tube 2 is passed through the through-hole. The reflection surface of the reflection ring 13 is made of a high-reflectivity, high-temperature resistant material, such as stainless steel. In this case, the roughness of the reflection surface of the reflection ring 13 is not greater than 0.1 microns. In some embodiments, the reflection surface of the reflection ring 13 is perpendicular to the axis m, and the reflection ring 13 blocks the gap between the thermal insulation shell 1 and the thermal expansion tube 2, thereby reducing the heat loss in the gap between the thermal insulation shell 1 and the thermal expansion tube 2. In some embodiments, the reflection surface is inclined from the direction away from the thermal insulation shell 1 to the direction close to the thermal expansion tube 2, reflecting heat radiation to the thermal expansion tube 2, further enhancing the reflection effect. It is worth noting that here, only the inclination angle of the reflection surface needs to be ensured, and there is no specific restriction on the external shape of the reflection ring 13.
[0044] Specifically, in some embodiments, a reflection ring 13 is provided at one end of the first insulation section 11 or at one end of the second insulation section 12, so that the heat near that end can be reflected back in a direction. Providing a reflection ring 13 at one end can simplify the structure of the insulation device, reduce the use of materials and the complexity of the manufacturing process, thereby reducing production costs. In some instances, a reflection ring 13 is provided at both ends of the insulation shell 1, and the inclination angles of the two reflection rings 13 are equal, forming a double heat reflection barrier. When thermal radiation radiates from the thermal expansion tube 2 to both ends, it is reflected back successively by the two reflection rings 13, reducing heat escape, greatly enhancing the insulation effect, and providing more comprehensive insulation protection for the thermal expansion tube 2. The reflection rings 13 at both ends can also make the temperature inside the thermal expansion tube 2 more uniform. Because heat is effectively reflected at both ends, the temperature distribution of the thermal expansion tube 2 along the axial direction is more stable.
[0045] Furthermore, the angle between the reflecting surface and the axis m of the thermal expansion tube 2 is greater than the angle A3 between the deformation section 22 and the axis m. That is, the reflecting surface is equivalent to a cover body provided at the end of the thermal insulation shell 1, thereby covering most of the gap between the end of the thermal insulation shell 1 and the thermal expansion tube 2, so that most of the heat can be reflected to the thermal expansion tube 2, reducing heat waste.
[0046] like Figure 2 As shown, for ease of description, the reflective ring 13 connected to the first insulation section 11 is referred to as the first reflective ring 131, and the reflective ring 13 connected to the second insulation section 12 is referred to as the second reflective ring 132. The first reflective ring 131 forms an angle B1 with the axis, while the second reflective ring 132 forms an angle B2 with the axis. Angle B1 is equal to angle B2, and the reflective rings 13 are symmetrical about the waistline N. The angle between the reflective rings 13 and the axis ranges from 45 to 50 degrees. A radial clearance of 20 to 40 mm is left between the reflective ring 13 and the outer surface of the thermal expansion tube 2 to facilitate placement of the thermal expansion tube 2 and the induction heating coil 3. The reflective ring 13 is fixedly connected to the insulation housing 1, for example, by riveting, welding, or bolting, without specific limitation herein.
[0047] Furthermore, the insulation device is provided with detection holes (not shown) to monitor the temperature of the deformable section 22, keeping track of temperature changes in the deformable section 22 and ensuring that the insulation device operates within a normal temperature range. Specifically, two to three detection holes are evenly spaced around the circumference of the first insulation section 11. These multiple detection holes provide a more comprehensive picture of the temperature of the deformable section 22. Detection holes in different locations can capture temperature changes in different areas, avoiding errors that may occur with single-point detection and ensuring more accurate temperature monitoring.
[0048] It is worth noting that the heat preservation device and diameter expansion device provided in this embodiment can be applied not only to steel pipes, but also to copper pipes or aluminum pipes, etc. The specific material of the pipe is not specifically limited here.
[0049] Obviously, the above-described embodiments of the present invention are merely examples for the purpose of clearly illustrating the present invention and are not intended to limit the manner in which the present invention is to be implemented. A person skilled in the art would be able to make various obvious changes, readjustments, and substitutions without departing from the scope of protection of the present invention. It is not necessary and impossible to enumerate all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the claims of the present invention.
Claims
1. A heat preservation device, characterized in that: include: A heat-insulating shell (1) is provided, wherein the heat-insulating shell (1) can be sleeved outside a heat-expanding tube (2) and an induction heating coil (3) and spaced apart from the heat-expanding tube (2); the induction heating coil (3) is located between the heat-insulating shell (1) and the heat-expanding tube (2); the heat-insulating shell (1) comprises a first heat-insulating section (11) and a second heat-insulating section (12) connected to each other; along the axial direction of the heat-expanding tube (2), the inner diameter of the first heat-insulating section (11) gradually decreases in a direction away from the second heat-insulating section (12); and the inner diameter of the second heat-insulating section (12) gradually decreases in a direction away from the first heat-insulating section (11).
2. The heat preservation device according to claim 1, characterized in that: The thermal expansion tube (2) comprises an introduction section (21), a deformation section (22) and a sizing section (23) which are arranged in sequence; the first heat preservation section (11) covers the deformation section (22) and a portion of the introduction section (21); and the second heat preservation section (12) covers a portion of the sizing section (23).
3. The heat preservation device according to claim 2, characterized in that: The first heat-insulating section (11) forms an angle A1 with the axis m of the thermal expansion tube (2), and the deformation section (22) forms an angle A3 with the axis m, where A1=A3.
4. The heat preservation device according to claim 3, characterized in that: The second heat preservation section (12) forms an angle A2 with the axis m, where A1 = A2.
5. The heat preservation device according to any one of claims 1 to 4, characterized in that: The heat-insulating device further comprises a reflection ring (13), and the reflection ring (13) is provided at least at one end of the heat-insulating shell (1), the heat-expanding tube (2) is passed through the reflection ring (13), and the reflection ring (13) is configured to reflect heat in the gap between the heat-insulating shell (1) and the heat-expanding tube (2).
6. The heat preservation device according to claim 5, characterized in that: The reflection ring (13) comprises a reflection surface and a through hole provided on the reflection surface, the thermal expansion tube (2) is passed through the through hole, and the reflection surface is inclined from a direction away from the heat-insulating shell (1) to a direction close to the thermal expansion tube (2).
7. The heat preservation device according to claim 6, characterized in that: The reflection rings (13) are provided at both ends of the heat-insulating outer shell (1), and the inclination angles of the two reflection rings (13) are equal.
8. The heat preservation device according to claim 6, characterized in that: The thermal expansion tube (2) comprises a deformation section (22), and an angle between the reflection surface and the axis m of the thermal expansion tube (2) is greater than an angle A3 between the deformation section (22) and the axis m.
9. The heat preservation device according to any one of claims 1 to 4, characterized in that: The heat-insulating device further comprises a reflective layer (14), the reflective layer (14) being arranged on the inner wall of the heat-insulating outer shell (1), and the reflective layer (14) being configured to reflect heat radiation onto the heat expansion tube (2).
10. A diameter expansion device comprising a conical core rod and an induction heating coil (3), wherein the conical core rod is configured to pass through a heat expansion tube (2), and the induction heating coil (3) can be sleeved outside the heat expansion tube (2) to heat the heat expansion tube (2), characterized in that: The heat preservation device comprises the heat preservation device according to any one of claims 1 to 9.